T-077: Rectangle-density lower bounds replayed at n=20, 42 and 70

V3 C3 lower bound confirmed superseded by T-090, T-091 and T-104

2026-10-02 published · wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · n=20,42,70

Three rectangle-density certificates in wand125/square-packing-bounds, raised on 2 October 2026, prove s(20)≥49/10 = 4.9, s(42)≥2731/400 = 6.8275 and s(70)≥3451/400 = 8.6275. Each raises the certificate T-068 reports at its count, which T-074 replayed, by 0.0025 to 0.0125.

Each is an exact nonnegative rational density on rectangles, D4-expanded, of mass n - 1/100, such that the shrunken core of every rotated unit square at each of 201 net directions captures mass at least one. The certificates were built with Tokoharu's solver, their weights scaled by one exact factor each to that mass. The same revision raised four more rungs, at n=59, 77, 91 and 93, which are below what this record holds there: the exact values s(59)=8 and s(77)=9, and the same revision's mixed certificates at n=91 and 92, the latter carried to n=93 (T-075).

Each passed a complete 201-direction replay here of Tokoharu's unchanged verify.cpp, in two cloud batches on 3 October 2026 whose receipts were merged into the packet on 6 October, and each replay reproduced the upstream accepting run's node count, leaf count and lower bound at every direction: confirmed, reproduced with the producer's code. The inputs were regenerated by this repository's exact preflight, which checks that each is the input the upstream accepting run recorded and checks the exact mass, net, smoothing and axis-event premises.

At n=20 and 42 the values raised the verified lower bound, from T-074's 1959/400 and 1363/200, and later on 6 October T-104's check2 certificate raised it again at n=20 and T-090's mixed certificate at n=42; at n=70 the mixed certificate of T-091 holds more.

Each was also decided by sqverify-fast, this repository's clean-room measure verifier, at all 201 net directions at Tokoharu's threshold 10001/10000 in the census of 3 October, and two mutants of each scaled below that threshold were refused on 6 October: confirmed, independently re-implemented as well. It shares no code with the source's checker and runs the same method, a second implementation and not a second method.

wand125 after Tokoharu and Levy, square-packing-bounds. No issue requests these certificates; the import of 2 October took them in from the source's own commits. The source says parts of the work were produced with AI assistance under human direction.

Significance, composition and next rung
Significance
Raised the verified lower bound at n=20 and 42, by 0.0025 and 0.0125 over T-074's replayed certificates, and the strongest rectangle-density lower bounds on record at all three counts. Raised rungs from one generator, as T-068's were, at S3; the 2 October review of the afternoon certificates proposed S3.
Composition
Three primary certificates at one source revision, each on its own count, with two complete replays each: the source's own checker, reproducing its records, and sqverify-fast on the census route for format T that the review of 6 October set and these certificates meet, an independent re-implementation. One interval-certified method: C3, and no second method.
Next rung
V4 and C4 need two adversarial AI reviews of this result by distinct reviewers and a human oversight record: the 2 October review of the afternoon certificates was the retaining lane's own and read them before the replays, and the 6 October review of the format T route decided the route, not these certificates' mathematics. A second machine method would be a method-distinct decision of rotated coverage; the source's C++ checker and sqverify-fast decide it by one method, and the exact preflight does not decide it.
Novelty
previously-published Present in an identified source

The cases

Case record

n=20

4.905
456
4.4725.472
nn+1

Proven

4.90500≤s(20)≤5

  • exact

Citation record n-020

lowerwand125 after Tokoharu, Levy et al. 2026, GitHub (confirmed T-104)

Open

  • optimality

The case record

LowerUpper
Gap19200= 0.095
Case record

n=42

6.847
678
6.4817.481
nn+1

Proven

6.84750≤s(42)≤7

  • exact

Citation record n-042

lowerwand125 after Tokoharu, Levy et al. 2026, GitHub (confirmed T-090)

Open

  • optimality

The case record

LowerUpper
Gap61400= 0.1525
Case record

n=70

8.658.881
8910
8.3679.367
nn+1

Proven

8.65750≤s(70)≤8.880961

  • exact

Citation record n-070

lowerwand125 after Tokoharu, Levy et al. 2026, GitHub (confirmed T-091)

upperry-xu 2026, GitHub (confirmed T-125)

Open

  • optimality

The case record

LowerUpper
Gap0.22346037…

Results on these cases

22 results in the register on n=20,42,70, oldest first, each with what it established and how it stands now.

  1. 2005 published T-007 · n=20,42,70

    s(n)≥min(⌈n⌉,n−2⌊n⌋+1+1) for 4≤n≤324

    V0 C1 lower bound incomplete on these cases, superseded by T-090, T-091 and T-104

    Nagamochi · Nagamochi 2005 · source · register

  2. 2026-09-04 established T-020 · n=20

    s(n)≥24/5=4.80 for n=19,20,21

    V3 C3 lower bound confirmed superseded by T-104

    Levy after Burns, Massaccesi · register

  3. 2026-09-04 published T-085 · n=20,42,70

    Nagamochi 2005, Lemma 1 is false for every container with a>3 and b>2

    V3 C3 correction confirmed

    Karakuş; chelokot · Karakuş 2026 · chelokot Nagamochi counterexample 2026 · packet · register

  4. 2026-09-05 established T-021 · n=20

    s(n)≥97/20=4.85 for n=20,21

    V3 C3 lower bound confirmed superseded by T-104

    Levy after Burns, Massaccesi · register

  5. 2026-09-22 published T-044 · n=70

    Weighted point lower bounds for ten counts in n=26…72, plus seven from the same files

    V3 C3 lower bound confirmed superseded by T-091

    wand125 after Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 point bounds 2026 · packet · source · review · register

  6. 2026-09-27 published T-045 · n=20

    Rectangle-density lower bounds replayed at 15 counts in n=18…78

    V3 C3 lower bound confirmed superseded by T-104

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026 · packet · packet · source · review · register

  7. 2026-09-27 published T-046 · n=20,42,70

    Rectangle-density lower bounds reported for 48 counts in n=18…95

    V0 C0 lower bound recorded superseded by T-090, T-091 and T-104

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026 · wand125 rectangle bounds 2026-09-28 · packet · packet · register

  8. 2026-09-28 published T-070 · n=42,70

    Rectangle-density lower bounds replayed at 25 counts in n=29…95

    V3 C3 lower bound confirmed superseded by T-090 and T-091

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026-09-28 · packet · packet · source · review · register

  9. 2026-09-29 published T-058 · n=20,42,70

    Rectangle-certificate ceiling α·UB(n) proved for n=1..100; B·UB(n) on 64 grid rows

    V3 C3 method limit confirmed

    wand125 after Tokoharu, Daniel · wand125 tools 2026 · packet · register

  10. 2026-09-29 published T-083 · n=20,42,70

    s(n)≥1/2+n−⌊n⌋+1/4 for every nonsquare 8≤n≤324

    V3 C3 lower bound confirmed on these cases, superseded by T-090, T-091 and T-104

    Karakuş · Karakuş 2026 · source · register

  11. 2026-10-01 published T-068 · n=20,42,70

    Rectangle-density lower bounds verified at 34 counts in n=19…95

    V3 C3 lower bound confirmed on these cases, superseded by T-090, T-091 and T-104

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026-10-01 · packet · source · review · register

  12. 2026-10-01 published T-074 · n=20,42,70

    Rectangle-density lower bounds replayed at 31 counts in n=19…95

    V3 C3 lower bound confirmed on these cases, superseded by T-090, T-091 and T-104

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026-10-01 · packet · packet · source · review · register

  13. 2026-10-02 published T-077 this result · n=20,42,70

    Rectangle-density lower bounds replayed at n=20, 42 and 70

    V3 C3 lower bound confirmed superseded by T-090, T-091 and T-104

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026-10-02 · packet · packet · source 1 · source 2 · review 1 · review 2 · register

  14. 2026-10-03 published T-082 · n=70

    Mixed rectangle-measure lower bounds verified at 22 counts in n=51…96

    V3 C3 lower bound confirmed on these cases, superseded by T-091

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 mixed bounds 2026-10-03 · packet · packet · source · review · register

  15. 2026-10-04 published T-090 · n=42

    Mixed rectangle-measure lower bounds verified at 17 counts in n=42…96

    V3 C3 lower bound confirmed

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 mixed bounds 2026-10-04 · packet · source · review · register

  16. 2026-10-04 published T-091 · n=70

    Mixed rectangle-measure lower bounds verified at 17 counts in n=53…95

    V3 C3 lower bound confirmed

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 mixed bounds evening 2026-10-04 · packet · source · review · register

  17. 2026-10-05 published T-101 · n=70

    Exact certificates of 77 catalogue packings: s(n) ≤ S', 1.2e-16 to 9.8e-15 above each side

    V3 C3 upper bound confirmed on these cases, superseded by T-125

    Daniel after Couzo, de Winter, Ellsworth, Levy · evand exact optima 2026-10-05 · packet · register

  18. 2026-10-06 published T-104 · n=20

    Mixed rectangle-measure lower bound verified at n=20, on a declared net

    V3 C3 lower bound confirmed

    wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 mixed bounds check2 2026-10-06 · packet · source · review · register

  19. 2026-10-07 published T-124 · n=20,42

    Reported non-strict local minima for 178 source configurations

    V0 C0 restricted optimality recorded

    Daniel after Couzo · Daniel exact and local reports 2026 · packet · register

  20. 2026-10-08 published T-125 · n=70

    Complete rational construction reports at 25 counts

    V3 C3 upper bound confirmed

    ry-xu · ry-xu square packing 2026 · packet · register

  21. 2026-10-10 published T-137 · n=70

    An exact rational refinement of Ryan Xu's packing of 70 squares

    V3 C3 upper bound confirmed

    Deleeuw after Xu, Levy · Deleeuw n70 refinement 2026-10-10 · packet · register

  22. 2026-10-10 published T-146 · n=70

    Exact rational certificates at fifteen counts from Evan Daniel's regularized record lists

    V3 C3 upper bound confirmed

    Daniel after Xu, Chaoweeraprasit, Mishapolk, Levy · Daniel regularized lists 2026-10-10 · packet · register