n = 84 open ★=
Proven
- new result
- exact
Citation record n-084
lowerwand125 after Tokoharu, Levy et al. 2026, GitHub (confirmed T-094)
upperStenlund 1980, Squares in Squares
Open
- optimality
Bounds
9.70710678118654
- Found by
- Evert Stenlund 1980
- Construction
- strip
- Source
- [Kingbird]
- Evidence
E-kingbird-upper-register,E-gobel-strip-upper
9.70710678118654752440084436210485
The reported value, verified here.
- Evidence
E-gobel-strip-upper
- Proved by
- wand125 2026
- Kind
- counting
- Scope
- Unrestricted unit-square packing with independent rotations and disjoint interiors.
- Note
- wand125's square-packing-bounds (5 October 2026) reports from a density of 686 uniform rectangles of total mass 8399999/100000, at core side 9977/10000 on 201 net half-angles, accepted there at every angle by its research copy of Tokoharu's verify.cpp at threshold one. It is above the 3763/400 of the source's mixed_n84_L94075 (T-090), which it supersedes. sqverify-fast decided it here on 5 October 2026 at all 201 net directions.
- Source
- [wand125 mixed bounds 2026-10-05]
- Evidence
E-n084-wand125-mixed-9411-report
The reported value, verified here.
≈ 0.29610678…
Verified upper minus verified lower.
Results in the register
T-007 V0 C1 Nagamochi · 2026-08-31 · 321 cases
for
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-071 V3 C3 wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · 2026-10-02 · n = 84–87
Mixed rectangle-measure lower bounds replayed at
Claim and records
- Claim
- Two rectangle densities of wand125/square-packing-bounds, checked at coverage one and published on 2 October 2026, prove = 9.4 and = 9.42. The certificate's mass is below 86 and 87 too, so it gives and as well: four counts in all.
Each certificate is a density of uniform rectangles with no point mass, of total mass n - 1/100000, at core side 9977/10000 on 201 net half-angles of step 83/40000: 661 rectangles at and 587 at . Each is accepted at every oblique net angle by code/mixed_rotated_verify.cpp, the research copy of Tokoharu's verify.cpp that the source's certificate (T-048) and the five certificates of T-069 use, which accepts coverage at least 1 where Tokoharu's requires 10001/10000, and at angle zero by exact integer tables. The least oblique lower bounds are 1.00000000089 at and 1.0000000017 at .
Both values exceed Green's reported 2 sqrt(2) + (247 + 12 sqrt(2))/41 = 9.2667335..., which this record holds at both counts by monotonicity from , by more than 0.1332 and 0.1532; the source's own improvement figures are measured from 9.2667, below Green's value, and are not lower bounds. At and 87 the value is also above the rectangle certificates T-068 reports there, 1873/200 and 941/100.
Each certificate passed a complete replay here on 2 October 2026 of the source's unchanged checker and per-angle functions on its pinned tarball: all 201 directions, each returning the certificate's own record. The replays run the source's own algorithm and are not an independent decision of coverage.
wand125 after Tokoharu and Levy, square-packing-bounds. Registration was requested in a comment of 2 October 2026 on jlevy/squares#282. The source says parts of the work were produced with AI assistance under human direction. - Composition
- Two primary certificates, each on its own reported entry and its own replay entry. and 87 take the certificate directly, its mass being below those counts, so no step is added. Each replay runs the source's C++ checker unchanged: one interval-certified method, replayed here, C3. Coverage is decided by that checker alone; the axis tables are a second implementation for one direction and not a second method.
- Next rung
- V4 and C4 need two adversarial AI reviews by distinct reviewers and a human oversight record; one adversarial review is retained. A second machine method would be a method-distinct decision of rotated coverage; the replays here run the source's own checker. The checker's controls were made on the certificate of the same kind.
- Significance
- Raised the verified lower bound at four counts, to 87, past Green's reported value at and 85 by the widest margins over it on record, by the certificate kind of T-048 and T-069. Further sizes from one generator at S3; the 2 October review of these certificates proposed S3, which the replays leave standing.
- Novelty
- previously-published Present in an identified source
- Records
n = 84n = 85n = 86n = 87registerevidence 1evidence 2evidence 3evidence 4sourcereview
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-090 V3 C3 wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · 2026-10-05 · 17 cases
Mixed rectangle-measure lower bounds verified at 17 counts in
T-094 V3 C3 wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · 2026-10-05 · n = 67, 84
Mixed rectangle-measure lower bounds verified at and
Claim and records
- Claim
- Two rectangle densities of wand125/square-packing-bounds, checked at coverage one and published on 5 October 2026, prove = 8.48 and = 9.411.
Each is a density of uniform rectangles in D4 orbits, 536 at and 686 at , and no point mass, of total mass n - 1/100000, at core side 9977/10000 on 201 net half-angles of step 83/40000, of the kind and checker of T-082, T-090 and T-091. The source reports each accepted at all 200 oblique net angles by code/mixed_rotated_verify.cpp, its research copy of Tokoharu's verify.cpp at coverage threshold one, and at the axis by exact integer tables. Both supersede the source's certificates of T-090 at the same count, mixed_n67_L8475 and mixed_n84_L94075.
Both values are above what the record held at their counts: the verified 1691/200 and 47/5, by 0.025 and 0.011, and T-090's reported 339/40 and 3763/400, by 0.005 and 0.0035. A packing of n + 1 squares contains one of n, but at and 85 the record already holds more in both lanes (851/100 and 473/50), so neither carries further.
Each certificate was decided here on 5 October 2026 by sqverify-fast, this repository's clean-room measure verifier, at all 201 net directions of the retained candidate, and two mutants of each scaled below coverage one were refused: confirmed, independently re-implemented. The verifier shares no code with the source's checker and runs the same net-and-shrink method, so it is a second implementation and not a second method. The source's own checker was not run here.
wand125 after Tokoharu and Levy, square-packing-bounds. Registration was requested in two comments of 5 October 2026 on jlevy/squares#282. The source says parts of the work were produced with AI assistance under human direction. - Composition
- Two primary certificates, each on its own reported entry and its own replay entry. Each replay is sqverify-fast at all 201 net directions of the retained candidate: one interval-certified method, replayed here by an independent implementation, C3. The source's checker and axis tables were not run here, so no second method and no reproduction with the producer's code stands beside it.
- Next rung
- V4 and C4 need two adversarial AI reviews by distinct reviewers and a human oversight record; one adversarial review is retained. A replay of the source's own checker, devtools.audit_wand125_point_and_mixed mixed-shard wand125-mixed-bounds-2026-10-05 --runners 2 (about 26.5 CPU-hours planned), would add a reproduction with the producer's code beside the rung; a second machine method would be a method-distinct decision of rotated coverage.
- Significance
- The strongest verified lower bounds on record at and 84, above the replayed rectangle and mixed certificates that held them by 0.025 and 0.011. Further sizes from the generator and checker of T-069, T-071, T-072, T-075, T-082, T-090 and T-091, with no new technique, at S3 as those are. The review of 5 October confirmed S3: that they are the source's first certificates verified here by an independently re-implemented replay is a fact about this repository's confirmation, not about the result.
- Novelty
- previously-published Present in an identified source
- Records
n = 67n = 84registerevidence 1evidence 2evidence 3evidence 4sourcereview
upper: replayed here; lower: replayed here
—
not rigid, numerically checked, numerical multiprecision
Evidence: E-translation-escape-not-rigid
Scope
Square 36 of the retained witness (witness id 37) translates 0.449747 along (-0.707107, -0.707107) with the packing still valid, so the configuration admits a non-trivial feasible motion; 6 of its 84 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.
- Blocker (source evidence): Green's reported lower-bound proof, cited as private communication by Friedman, has not been recovered or independently replayed.
E-green-ds7-theorem9-reported-lower
12 evidence entries
E-n084-wand125-mixed-9411-sqverify-fast-replay, E-n084-wand125-mixed-94075-sqverify-fast-replay, E-n084-wand125-mixed-9411-report, E-n084-wand125-mixed-940-source-replay, E-n084-wand125-mixed-940-report, E-kingbird-upper-register, E-nagamochi-lower, E-basic-grid-upper, E-karakus-strip-lower, E-nagamochi-lemma1-counterexample, E-gobel-strip-upper, E-green-ds7-theorem9-reported-lower
- [wand125 mixed bounds 2026-10-05] lower bound proof
- [wand125 mixed bounds 2026-10-04] lower bound proof
- [wand125 mixed bounds 2026-10-02] lower bound proof
- [Kingbird] record catalogue
- [Nagamochi 2005] lower bound proof
- [Friedman DS7] survey
- [Karakuş 2026] lower bound proof
— open
External intake, 2026-10-05 (certificate of 5 October). wand125’s
mixed-certificate source
reports (T-094), from a density of 686 rectangles of total
mass , accepted there at every net angle by its research copy of
Tokoharu’s checker at threshold one.
It is above the source’s of the day before, by , and the verified
by . It supersedes the source’s mixed_n84_L94075 (T-090). sqverify-fast,
this repository’s clean-room verifier, decided it here on 5 October 2026 at all 201 net
directions, so it is also the verified lower bound: confirmed, independently
re-implemented. wand125’s README says parts of the work were produced with AI assistance
under human direction.
External intake, 2026-10-05 (certificate of 4 October). wand125’s
mixed-certificate source
reports the mixed certificate mixed_n84_L94075 at side (T-090),
since superseded (T-094), from a density of 569 rectangles of total mass
, accepted there at every net angle by its research copy of
Tokoharu’s checker at threshold one.
It is above the this case reported, by . It supersedes the source’s
mixed_n84_L940. sqverify-fast, this repository’s clean-room verifier, decided it here
on 6 October 2026 at all 201 net directions: confirmed, independently re-implemented.
The verified lower bound is unchanged, the certificate above being higher.
wand125’s README says parts of the work were produced with AI assistance under human
direction.
External intake, 2026-10-02. wand125’s
mixed-certificate source
reports the mixed certificate mixed_n84_L940 at side (T-071), since
superseded (T-090), from a density of 661 rectangles of total mass
, accepted there at every net angle by its research copy of
Tokoharu’s checker at threshold one.
It is above Green’s reported , which this case held by monotonicity, by
more than . Its complete replay here on 2 October 2026 returned the
certificate’s own record at all 201 directions, so it was the verified lower bound until
5 October.
wand125’s README says parts of the work were produced with AI assistance under
human direction.
Open. The best known packing gives , and the verified lower bound is , from wand125’s mixed rectangle-density certificate of 5 October, leaving a gap of .
The packing
Found by Frits Göbel in 1979, via a diagonal-strip construction — the strip family at
, whose side is exactly.
cases/gobel_strip builds it and verifies it exactly over Q(sqrt 2), which is what
moved verified_upper_bound from the grid ceiling onto the exact side.
The retained witness declares that side rounded down at its own digits — about
below the exact value — and a different slack choice for the strip, so the
certificate carries the construction’s coordinates rather than the witness’s (D-398).
The lower bound
Before 2 October the selected external report was [Friedman DS7], which gives the lower-bound expression for (approximately ). Friedman’s DS7 survey, Theorem 9, k=9, reports this bound at n=82; reference [8] is Green’s private communication (2000). The source proof has not been recovered. The unavoidable-set argument DS7’s Figure 34 illustrates does not prove it: at that point pattern leaves a unit square empty (review). Inherited at n=84 by monotonicity. That changed the reported source field only; the verified field now holds wand125’s replayed mixed certificate. The source audit compares the exact theorem expressions separately from opaque table decimals.
The verified field rests on a complete decision here
(E-n084-wand125-mixed-9411-sqverify-fast-replay, V3/C3) of
wand125’s mixed certificate of 5 October by sqverify-fast, this repository’s clean-room
measure verifier: all 201 net directions of the retained candidate on 5 October 2026,
with two mutants scaled below coverage one refused.
It shares no code with the source’s checker, so it decides coverage a second way with
the same method; the source’s own checker was not run here.
From 2 October 2026 until this decision the verified field rested on a complete replay
here (E-n084-wand125-mixed-940-source-replay) of the source’s
certificate mixed_n84_L940, at : the source’s unchanged checker and per-angle
functions on the pinned bundle, all 201 directions, each returning the certificate’s own
record.
Until 2 October 2026 the verified lower bound was Nagamochi’s general closed form, now a reported bound (see the correction below). Karakuş’s general bound, independently verified here and below this certificate at this , applies to every nonsquare :
Correction, 2 October 2026. Until that date the verified lower bound here was Nagamochi’s general closed form, , which is stronger at this and is now recorded as a reported bound. Its published proof rests on Nagamochi’s Lemma 1, which Karakuş showed false; nothing is disproved, and no packing beating it is known (review of 2 October 2026). This register had recorded that proof as verified, its own error, logged as defect D-516.
See the Frontier corpus summary for the current aggregate count; source-reported bounds are recorded separately.
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-n084-wand125-mixed-9411-sqverify-fast-replay |
replayed here | independent | V-sqverify-fast (first-party) |
| verified upper | E-gobel-strip-upper |
replayed here | independent | V-sqpack-verify (first-party) |