n = 12 open ★=
Proven
- new result
- exact
Citation record n-012
lowersquarepacker after Daniel, Levy 2026, GitHub (confirmed T-095)
Open
- optimality
Bounds
- Proved by
- squarepacker (Ryu Sungjoon) 2026
- Kind
- counting
- Scope
- Unrestricted independent rotations with disjoint interiors; boundary contact allowed.
- Note
- squarepacker/s12-lower-bound v1.1 (5 October 2026) states = 3.9715 from Evan Daniel's 1,736 points dilated to the container 7943/2000 and rounded one D4 orbit at a time, with new weights found by linear programming after this project's Route B, total weight 11.9974808, checked at the angle net by Daniel's Rust verifier with overflow checks and by the author's own indep_check.cpp; both refuse it at , which a pass at one net does not need. Reported on jlevy/squares#363 and archived on Zenodo.
- Source
- [squarepacker s12 2026-10-05]
- Evidence
E-n012-squarepacker-7943-2000-report
The reported value, verified here.
= 0.0285
Verified upper minus verified lower.
Results in the register
T-007 V0 C1 Nagamochi · 2026-08-31 · 321 cases
for
T-017 V3 C3 Levy after Burns, Massaccesi · 2026-09-04 · n = 12
Claim and records
- Claim
- , by this project's weighted fractional unavoidable-set certificate at container side 99/25 = 3.96.
This is the first lower bound specific to in the retained corpus: the case previously held 2 + 4/sqrt(5) = 3.788854..., which is Stromquist's bound inherited by monotonicity and says nothing about twelve squares in particular. The movement is +0.171146, and the case stays open against its conjectured optimum of 4, now by 0.04. Seven rungs are retained below it, 19/5 through 79/20.
It also separates the two cases for the first time. The retained side exceeds Trump's 1979 packing of eleven squares at 3.877084, so > strictly, by at least 0.082916. Monotonicity gives only >= ; the strict inequality did not follow from anything on record before, because 's previous lower bound was 's own 3.788854 and sat below Trump's packing. - Composition
- Primary: one certificate, one verifier, one accepted verdict. The bound is the certificate's container side directly, with no monotonicity or composition step between the artifact and the claim.
- Next rung
- Two machine methods decide it. The independent re-derivation agrees but is exact-algebraic like the first; the second method is the interval-certified decision, which bounds coverage by branch and bound over boxes of centres with directed rounding: the two routes share the certificate and the closed-form conditions, and share no part of how Condition 5 is decided. The register shows the two methods beside the rung. V4 and C4 need two adversarial AI reviews by distinct reviewers and a human oversight record, and none is retained.
The bound itself: the ladder 19/5, 77/20, 97/25, 39/10, 393/100, 197/50, 79/20, 99/25 was climbed once the separation oracle was corrected to score the cells the verifier decides (D-434), and every rung is retained.
The retained certificate's total is 149987/12500 = 11.998960, leaving 0.001040 below twelve -- the tightest margin of any rung in the record, and it survived on the sign of a rounding rather than by design. The next tightest, two rungs below at 197/50, is about seven times wider.
Rationalisation rounds each orbit up to a multiple of 1/scale, so its cost is at most atoms/scale; at 2097 atoms and scale 200,000 it took 0.005314, five times what remained. Raising the scale twentyfold would have cost about 0.00027 and would not have changed the atom count. That is a defaults question and it is BC-191's.
Margin does not shrink monotonically as the ladder climbs -- the 197/50 rung two below this one has 0.007175 and 79/20 has 0.029410, so a tight rung is evidence about that run and not about how much room is left.
This rung also cost the exhaustive tier, when it was retained: 2097 atoms is 1.8 times the next largest retained certificate, the 1184-atom rung, and the exact sweep is quadratic in the atom count, so deciding it took 4866 s where the interval route took 110 s. The sweep was rewritten the same day to decide in integers on the weights' common scale, in parallel over directions, and returns the same verdict in well under a minute; BC-195 owns whether the tier can still afford what it holds.
What is left is bounded, though, and by the method rather than by the search. A certificate for n cannot exist above ceil(sqrt(n)) * B, since a container wider than that holds ceil(sqrt(n))^2 pairwise disjoint axis-parallel B-squares, each carrying mass at least 1 by Condition 5, which forces the total past n and breaks Condition 2. Here that ceiling is 4B = 3.9908 on this certificate's own B, and it is what binds: 4/(1 + D) = 3.990816 is the supremum over every shrink the 181-direction net admits, and the grid packing's 4 sits above both. So the retained 99/25 has 0.0308 of runway left.
The consequence for this case is structural and worth stating exactly: the grid packing gives , the ceiling sits strictly below 4, and 4 is the conjectured value -- so no single certificate of this shape certifies , however fine the net or the site set. What the ceiling does not exclude is a proved family of certificates with sides tending to 4 and a limit argument on top of it; whether such a family exists is a question about the covering value, and an earlier version of this sentence overstated the ceiling into a method-wide impossibility (PR 78's adversarial review, F14). What remains is how close to 4 a certificate can get. - Significance
- Scored against the rubric's anchor for S4, "a reusable technique, bound family, or resolved disputed value". What is retained is not one bound but an eight-rung ladder -- 19/5, 77/20, 97/25, 39/10, 393/100, 197/50, 79/20, 99/25 -- by a generator that applies at every n and that has since produced the result as well, so this is a bound family rather than a case result.
It is also the first bound located in the retained corpus that is proved about rather than inherited from : the frontier case body had recorded that nothing specific to had been proved there.
Held below S5 because is not a central open case, weighted resource counting predates this project, the recent pure-atomic rational direction-net architecture follows Burns, the LP parameter line follows Massaccesi, the second exact check shares a method family with the first, and the gap to the conjectured 4 is 0.04, which this approach does not close. - Novelty
- apparently-novel Not found in the recorded search, subject to its stated gaps
- Records
T-049 V3 C3 Daniel after Burns, Massaccesi · 2026-09-29 · n = 12
Claim and records
- Claim
- = 3.9686155..., by Evan Daniel's weighted point certificate, published on 25 August 2026 and first seen here on 27 September. It raised the verified bound by 851/98775, about 0.0086, over T-017.
The certificate is 1,736 D4-invariant rational points of total weight 11.9738036 < 12 such that every closed unit square in [0, 15680/3951]^2, at every angle, captures weight at least one, decided over the rational angle net 2 arctan(k/6000) with a per-bin shrink of 1/(cos d + sin d).
It was replayed here on 27 September 2026 by the source's Rust arrangement-sweep verifier at , least captured weight 10000056/10^7 at bin 0 as the source records, and by its exact Python re-check on 50 bins. It was also decided completely by this repository's native parent-core interval branch and bound over all 2,486 rows, which shares nothing with the source's sweep and gives the strict .
Evan Daniel, evand/square-packing (formerly square-packing-12), building on Sam Burns's and Gustavo Massaccesi's weighted exact-rational covering method. The source's CREDITS.md says the work was produced with an AI agent under human direction. - Composition
- Primary at : one certificate, no monotonicity. Two entries whose methods differ decide it, the source's exact arrangement sweep (exact-algebraic, replayed here) and this repository's directed-rounding interval coverage of every row (interval-certified); that is C3, with the two methods shown beside the rung. Both rest on the source's certificate and the same counting theorem, and the thin reader that maps the source's integer file onto parent-core rows has had no review reading of its own.
- Next rung
- A review reading of the native reader (devtools.verify_evand_angle_net_native) would close the one unread link in the second method's route. V4 and C4 need two adversarial AI reviews by distinct reviewers and a human oversight record, and none is retained; whether a mapped same-project review of another author's result counts toward them is the owner's decision. Rung 5 needs a proof-assistant formalization reviewed by human experts. The exact value remains open; the conjecture is .
- Significance
- Raised the verified lower bound at by 0.0086 to within 0.0314 of the grid's 4, on two methods. The method is Burns's and Massaccesi's, as this repository's own ladder is; the instance is new. A substantive case result, S3. It entered its source ten days before T-017 was scored, which bears on T-017's "first lower bound specific to " (the plan's open question 3) but not on this score.
- Novelty
- previously-published Present in an identified source
- Records
n = 12registerevidence 1evidence 2evidence 3source 1source 2review 1review 2
T-058 V3 C3 wand125 after Tokoharu, Daniel · 2026-09-29 · 100 cases
Rectangle-certificate ceiling
α·UB(n)proved for ..100;B·UB(n)on 64 grid rowsT-078 V3 C3 squarepacker after Daniel · 2026-10-03 · n = 12
, Daniel's certificate rescaled by
Claim and records
- Claim
- = 3.96911783..., by squarepacker (Ryu Sungjoon) after Evan Daniel, published on 2 October 2026 and reported on jlevy/squares#309. It raises the verified bound by 15680/31216851, about 0.000502, over T-049.
The certificate is Daniel's 1,736-point weighted certificate of T-049 with every coordinate and the container multiplied by 7902/7901 and the weights unchanged, total 11.9738036 < 12. The rescaling and its verification on the finer angle net are squarepacker's; the certificate and the verifier that decides it are Daniel's. Every closed unit square in [0, 31360/7901]^2, at every angle, captures weight at least one, decided over the rational angle net 2 arctan(k/24000) with a per-bin shrink of 1/(cos d + sin d). The nets and 12000 refuse it, which a pass at one net does not need: each net's test is a complete sufficient condition.
It was replayed here on 2 October 2026 by Daniel's verifier and by squarepacker's own indep_check.cpp at , least captured weight 10000056/10^7 at bin 0 in both, as the source records, and decided completely by this repository's native parent-core interval branch and bound over all 9,942 rows, which shares nothing with the two sweeps and gives the strict .
squarepacker (Ryu Sungjoon), s12-lower-bound, archived as Zenodo 10.5281/zenodo.23106582, after Evan Daniel's certificate and verifier (T-049). The source's README says the rescaling, the verification runs and its checker were prepared with the help of an AI assistant from Anthropic, which it names. - Composition
- Primary at : one certificate, no monotonicity. Two entries whose methods differ decide it: the producer's two arrangement sweeps, Daniel's verify and squarepacker's indep_check.cpp (exact-algebraic, replayed here, one method in two implementations), and this repository's directed-rounding interval coverage of every row (interval-certified); that is C3, with the two methods shown beside the rung. All three rest on the certificate, the counting theorem and the shrink lemma on the net , and the native rows are Daniel's bins and sigma_k by design.
- Next rung
- V4 and C4 need two adversarial AI reviews by distinct reviewers and a human oversight record; the one retained review was written by the lane that ran the replays, so a separately prompted read is the next step. Rung 5 needs a proof-assistant formalization reviewed by human experts; the source notes that Daniel's Lean pose-box-tree checker, which kernel-checks T-049's certificate, could in principle take this one. The exact value remains open; the conjecture is .
- Significance
- True and replayed in full by three checkers, and it raises the verified lower bound at , but by 0.000502, moving the gap to the grid's 4 from 0.0314 to 0.0309. It rescales T-049's certificate until a finer angle net stops accepting it, which spends that certificate's slack and adds no technique, as the source says itself; T-061 is the precedent for scoring such a step by what it changes.
- Novelty
- previously-published Present in an identified source
- Records
n = 12registerevidence 1evidence 2evidence 3source 1source 2review 1review 2
T-079 V3 C3 Levy after Daniel · 2026-10-03 · n = 12
, Daniel's points re-weighted
Claim and records
- Claim
- = 3.97020020..., by re-weighting Evan Daniel's 1,736 points. It raises the verified lower bound by 33774720/31204391123, about 0.0010824, over squarepacker's (T-078), and leaves a gap of 117692/3949423, about 0.0298, to the grid's 4.
The certificate keeps the points of Daniel's certificate (T-049), every coordinate scaled by 3951000/3949423, and solves for new weights by linear programming over their 223 D4 orbits, with rows from the near-tight cells Daniel's verifier reports; the total is 14970347/1250000 = 11.9762776 < 12. Every closed unit square in [0, 15680000/3949423]^2, at every angle, captures weight at least one, decided over the rational angle net 2 arctan(k/96000) with Daniel's per-bin shrink.
It was decided here three ways on 2 and 3 October 2026: by Daniel's verifier, built unmodified with overflow checks on, in the producing run and again by a review lane that did not produce it, both VERIFIED over all 39,765 bins, least captured weight 10000045/10^7; and by this repository's parent-core interval branch and bound over all 39,765 rows, which shares no code with the sweep or with the LP and gives the strict . Both checkers refuse two mutated certificates.
This project's re-weighting, after Evan Daniel's certificate and verifier (T-049), whose method is Burns's and Massaccesi's, and after squarepacker's rescaling of that certificate (T-078), which showed a finer net leaves room for a larger container. The same work rescaled Daniel's certificate whole to , which this bound implies. - Composition
- Primary at : one certificate, no monotonicity. Two methods decide it: Daniel's arrangement sweep (exact-algebraic), run by the producing lane and replayed by the review lane, and this repository's directed-rounding interval coverage of every row (interval-certified); that is C3, with two methods shown beside the rung. The exact audit of the file is a premise check, well-formedness only, and decides nothing. All rest on the certificate, the counting step and the shrink lemma on the net , and the native rows are the sweep's bins and sigma_k by design.
- Next rung
- V4 and C4 need a second adversarial AI review by a distinct reviewer and a human oversight record. Rung 5 needs a proof-assistant formalization reviewed by human experts; Daniel's Lean pose-box-tree checker, which kernel-checks T-049's certificate, could in principle take this one. The same 1,736 points carried the bound further: the LP total was 0.024 below 12 at this side, and squarepacker's re-weighting of them reached 7943/2000 (T-095). The exact value remains open; the conjecture is .
- Significance
- Raises the verified lower bound at again, by 0.0016 over Daniel's T-049 and 0.0011 over T-078, to within 0.0298 of 4, the best verified bound at this repository knows of. T-049, which raised it by 0.0086, is S3, and the step here is new weights on Daniel's geometry, not a rescaling alone. Not S4: the method, a weighted cover re-optimised at a finer net, is Daniel's, Burns's and Massaccesi's. Not S5: pure point covers are capped well short of 4, so the central question at does not move.
- Novelty
- apparently-novel Not found in the recorded search, subject to its stated gaps
- Records
n = 12registerevidence 1evidence 2evidence 3evidence 4source 1source 2review
T-083 V3 C3 Karakuş · 2026-10-02 · 301 cases
for every nonsquare
T-085 V3 C3 Karakuş; chelokot · 2026-10-02 · 315 cases
Nagamochi 2005, Lemma 1 is false for every container with and
T-095 V3 C3 squarepacker after Daniel, Levy · 2026-10-05 · n = 12
, Daniel's points dilated and re-weighted
Claim and records
- Claim
- = 3.9715, by squarepacker (Ryu Sungjoon) after Evan Daniel and this project's Route B (T-079), published on 5 October 2026 as release v1.1 of squarepacker/s12-lower-bound and reported on jlevy/squares#363. It raises the verified lower bound by 10266889/7898846000, about 0.0013, over T-079's 15680000/3949423, and leaves 57/2000 = 0.0285 to the grid's 4.
The certificate keeps Daniel's 1,736 points of T-049, dilated by 31382793/31360000 to the container 7943/2000 and rounded to the grid 1/4000000 one D4 orbit at a time, every coordinate within 11/39200000 of its exact image, with new weights found by linear programming: all 223 orbits positive, total 119974808/10^7 = 11.9974808 < 12. Every closed unit square in [0, 7943/2000]^2, at every angle, captures weight at least one, decided over the rational angle net 2 arctan(k/96000) with Daniel's per-bin shrink. The nets and 48000 refuse it, which a pass at one net does not need.
It was decided here on 5 October 2026 by Daniel's verifier, reproduced with the producer's code: built from the retained source with overflow checks on, VERIFIED over all 39,765 bins, least captured weight 10000050/10^7 at bin 0, every line as the source's log; and independently re-implemented by this repository's parent-core interval branch and bound over all 39,765 rows, which shares no code with the sweep or with the search that made the weights and gives the strict . squarepacker's own indep_check.cpp, replayed here at and 192000 with the source's minimum, is the producer's evidence: the search stopped when its range-restricted copy found no violation. All three refuse the source's two altered certificates.
squarepacker (Ryu Sungjoon), s12-lower-bound, archived as Zenodo 10.5281/zenodo.23157015, after Evan Daniel's points and verifier (T-049) and this project's re-weighting of them (T-079), whose tool the source says guided its own scripts, written from scratch. The source says the rescaling, the re-weighting, the verification runs and its tools were prepared with the help of Claude (Anthropic). - Composition
- Primary at : one certificate, no monotonicity. Two methods decide it: Daniel's arrangement sweep (exact-algebraic), the producer's verifier replayed here in full with overflow checks, and this repository's directed-rounding interval coverage of every row (interval-certified), which shares no code with it or with the search that made the weights; that is C3, with two methods shown beside the rung.
squarepacker's indep_check.cpp, replayed here too, is a second implementation of the sweep's method and the producer's own, and its range-restricted copy was the search's stopping rule, so it is producer evidence and confirms nothing beyond the other two (review F3). The exact audit of the file is a premise check and decides nothing. All rest on the certificate, the counting step and the shrink lemma on the net , and the native rows are the sweep's bins and sigma_k by design (review F9). - Next rung
- V4 and C4 need a second adversarial AI review by a distinct reviewer and a human oversight record; the one retained review read the argument and computed nothing (its F1), so a second one that runs its own exact checks would add most. Rung 5 needs a proof-assistant formalization reviewed by human experts; Daniel's Lean pose-box-tree checker, which kernel-checks T-049's certificate, could in principle take this one, as the source notes. The source's own analysis puts re-weighting of these points near its end below 560/141 = 3.97163; a higher bound needs new points or another method, and point covers stop short of 3.99. The exact value remains open; the conjecture is .
- Significance
- Raises the verified lower bound at by 0.0013 over T-079, the largest step since T-049. New weights on Daniel's points by T-079's recipe, Route B, with a complete scan in every cycle of the search, so no new technique and not S4; T-078, a rescaling, is S2, and T-079, new weights, is S3. Its source shows these points nearly exhausted for re-weighting, about 1.3e-4 below 560/141, which answers T-079's open "the same points may carry the bound further". Not S5: point covers are capped below 3.99.
- Novelty
- previously-published Present in an identified source
- Records
n = 12registerevidence 1evidence 2evidence 3evidence 4source 1source 2review 1review 2
upper: replayed here; lower: replayed here, audited here
—
not rigid, numerically checked, numerical multiprecision
Evidence: E-translation-escape-not-rigid
Scope
Square 8 of the retained witness (witness id 9) translates 1 along (0, 1) with the packing still valid, so the configuration admits a non-trivial feasible motion; 4 of its 12 squares do. Every constraint is exactly affine in the slide parameter, so the arithmetic carries no linearization error, but the coordinates are the witness's own finite-precision transcription: this settles the retained configuration, not the true optimum. Rigidity and optimality are independent, and this bears only on the former.
20 evidence entries
E-kingbird-upper-register, E-n012-monotonicity-lower, E-basic-grid-upper, E-n012-independent-verifier, E-n012-fractional-certificate, E-fractional-interval-decision, E-n012-evand-15680-3951-report, E-n012-evand-15680-3951-source-replay, E-n012-evand-15680-3951-native-parent-core, E-n012-squarepacker-31360-7901-report, E-n012-squarepacker-31360-7901-source-replay, E-n012-squarepacker-31360-7901-native-parent-core, E-n012-levy-15680000-3949423-generator, E-n012-levy-15680000-3949423-source-replay, E-n012-levy-15680000-3949423-native-parent-core, E-n012-levy-15680000-3949423-audit, E-n012-squarepacker-7943-2000-report, E-n012-squarepacker-7943-2000-source-replay, E-n012-squarepacker-7943-2000-native-parent-core, E-n012-squarepacker-7943-2000-audit
- [squarepacker s12 2026-10-05] lower bound proof
- [squarepacker s12 2026] lower bound proof
- [Kingbird] record catalogue
- [Stromquist 2003] lower bound proof
- [evand square-packing 2026] lower bound proof
- [Friedman DS7] survey
— open, with a verified lower bound
The trivial 4×4 grid gives , and no retained verified construction improves
it. The exact value remains open; this record does not assign a probability to the
conjecture . The verified lower bound is
(T-095), squarepacker’s (Ryu Sungjoon’s) release v1.1 of
s12-lower-bound,
published on 5 October 2026: Evan Daniel’s 1,736 points below, dilated to the container
and rounded to the grid one symmetry orbit at a time, with new
weights found by linear programming after this project’s Route B, all 223 orbits
positive, total . It leaves the case open by
against its conjectured optimum.
Its README credits the points, the verifier and the reduction to Daniel and the
re-weighting idea to this project, and says the re-weighting, the verification runs and
its tools were prepared with the help of Claude (Anthropic).
Daniel’s verifier, built from the retained source with overflow checks on, accepts it
over all 39,765 bins of the net , least captured weight at
bin 0, in a replay here on 5 October that printed every line of the source’s log
(E-n012-squarepacker-7943-2000-source-replay); squarepacker’s own
tools/indep_check.cpp accepts it at and with the same minimum.
The source stopped its weight search when a range-restricted copy of indep_check found
no violation, so those runs are the producer’s evidence, and the decisive second check
is this repository’s parent-core interval route, which shares no code with either and
certified all 39,765 rows
(E-n012-squarepacker-7943-2000-native-parent-core). All three refuse
the source’s two altered certificates.
The nets and refuse the certificate, which a pass at one net does
not need. The
review, prompted
separately and blind to the replay, re-derives the argument and finds no blocking
defect; it ran no computation of its own.
Until 5 October the verified lower bound was (T-079),
this project’s re-weighting of the same points, which v1.1 follows: Daniel’s points
scaled by , with new weights found by linear programming over their
orbits, total
(certificate and receipts). Daniel’s
verifier, built unmodified with overflow checks on, accepts it over all 39,765 bins of
the net , least captured weight at bin 0, in the producing
run and again by a review lane that did not produce it
(E-n012-levy-15680000-3949423-source-replay). Because the weights
were fitted against the cells that verifier reports, the decisive second check was this
repository’s parent-core interval route, which certified all 39,765 rows
(E-n012-levy-15680000-3949423-native-parent-core). Both refuse two
mutated certificates, and the
review
accepts the bound with no blocking finding.
It stays true as stated.
Until 3 October the verified lower bound was (T-078),
squarepacker’s (Ryu Sungjoon’s)
s12-lower-bound,
published on 2 October 2026: Evan Daniel’s weighted certificate below with every
coordinate and the container multiplied by and the weights unchanged.
Its README credits the certificate and the verifier to Daniel, and says the rescaling,
the verification runs and its own checker were prepared with the help of an AI assistant
from Anthropic.
The rescaled certificate is refused by the angle nets and and
accepted at , least captured weight at bin 0; a pass at any
one net is a complete check, so the refusals are not counterexamples.
That pass was replayed here on 2 October by Daniel’s verifier and by squarepacker’s own
tools/indep_check.cpp
(E-n012-squarepacker-31360-7901-source-replay), and this repository’s
parent-core interval route decided all 9,942 rows of the finer net completely
(E-n012-squarepacker-31360-7901-native-parent-core), which gives the
strict . All three refuse two mutated certificates.
The one retained
review was
written by the lane that ran the replays, its finding F1, so it is that lane’s own read
and not a separately prompted one.
Until 3 October the verified lower bound was Evan Daniel’s ,
from
evand/square-packing,
which builds on Sam Burns’s and Gustavo Massaccesi’s weighted exact-rational covering
method; its CREDITS.md says the work was produced by Claude (Anthropic) in a single
session under human direction.
Its certificate entered the source on 2026-08-25, but this record first saw it on
2026-09-27.
The certificate is 1,736 rationally weighted points in , total weight
, such that every closed unit square in the container, at every angle,
captures weight at least . The source’s Rust verifier decides that over a rational
angle net at , shrinking each bin’s square by ;
the least captured weight is . That verifier was replayed here from the
retained bytes at , reproducing that minimum at the same bin, and the source’s
independently written exact Python re-check was run on a sample of its bins
(E-n012-evand-15680-3951-source-replay). A
review of 27 September
found the bound sound as stated.
This repository’s own parent-core interval route then decided the same certificate
completely: all 2,486 angle rows, read as parent-core rows with parent side , certify
at one unit by directed-rounding branch and bound over centre boxes, with no stalled box
(E-n012-evand-15680-3951-native-parent-core). That decision shares
nothing with the source’s arrangement sweep, so that bound stood at V3/C3 on two
machine methods; both rest on the source’s certificate and the same counting theorem,
and the reader that maps its file onto the rows has not yet had a review reading of its
own. The method is Burns’s and Massaccesi’s, as this repository’s own ladder below is;
what is new is the instance.
The current strategy treats as Route N: high exact-value upside but lower readiness than the selected Route A. A new block becomes competitive only after it states one uniform boundary-capacity or deformation lemma over a nontrivial interval and includes the flexible side-four boundary strata. See the post-W5 route selection.
Before 2026-09-27 the verified bound was this repository’s own
(T-017), the first bound proved about twelve squares rather than
inherited from . It remains valid and is kept with its ladder: 2,097 weighted
atoms on a D4-symmetric grid, total mass , every placement of a shrunken
square covering mass at least , and seven earlier rungs, through
, reached by the same instrument.
Condition 5 is decided twice from its bytes, by the exact event-cell sweep and by a
method-distinct interval branch and bound.
Before that the case had only , Stromquist’s bound carried here by
monotonicity.
Why 12 is harder to prove than 13, which is already solved
This inverts the usual intuition and is the single most useful fact about this case. was proved by Bentz in 2010. Since twelve squares are easier to pack than thirteen, proving is a strictly stronger statement: a lower-bound argument must exclude packings of squares, and excluding twelve from a side-4 container rules out strictly more configurations than excluding thirteen. The unavoidable-point method’s difficulty scales with how few squares must be excluded.
So the open region does not begin and end at 11. It begins at 11 and continues at 12, and 12 is the case where the existing technique comes closest to reaching.
Why it is the recommended first computational target
The conjectured optimum is an integer, which sidesteps the specific obstruction at : no high-degree algebraic threshold needs certifying, only the integer . Every rigorous technique in the literature certifies thresholds built from unit distances and container coordinates, and an integer target is exactly what they handle. Combined with a container of modest size, is the most plausible place for the first new proved value of since 2018.
A caution against assuming the answer
Secondary summaries sometimes assert on the ground that “12 squares fit in a
4×4 arrangement” — which establishes only . And plausible patterns in this
subject fail late: the conjecture survived in print to , where
Cleemann packed 272 unit squares into a side-17 square with room to spare — and the
retained catalogue has since pushed the boundary to : Hajba (2015) at ,
Arslanov (2019) at , and Cantrell (February 2025) at , whose retained
witness (n-110) sits at side . An
unbeaten grid is evidence, not proof.
Verification Code
The programs behind this case’s verified bounds, by their evidence.
The code column says how the code that ran stands to the code its producer used.
VERIFIERS.md says what each program is and whose it is.
| bound | evidence | run | code | programs |
|---|---|---|---|---|
| verified lower | E-n012-squarepacker-7943-2000-source-replay |
replayed here | producer’s code | V-evand-angle-net-verify, V-squarepacker-indep-check-cpp (external) |
| verified lower | E-n012-squarepacker-7943-2000-native-parent-core |
audited here | independent | V-sqpack-parent-core-native (first-party) |
| verified upper | E-basic-grid-upper |
replayed here | independent | V-check-basic-bounds (first-party) |