T-204: Mixed rectangle-measure lower bound s(51)≥3011/400 reported, on a 2,073-direction declared net

V0 C0 Lower bound recorded

2026-10-16 published · Hosono after Tokoharu and Levy · n=51

A rectangle measure of wand125/square-packing, published on 16 October 2026 and reported in jlevy/squares#446, is reported to prove s(51)≥3011/400 = 7.5275.

The certificate, mixed_n51_L75275, is a density of 908 uniform rectangles in D4 orbits, and no point mass, of total mass 5099999/100000, on a net its candidate declares: core side 4999/5000 and 2,073 half-angle tangents of step 1/5002, the net of T-132, T-142 and T-143. Since 4999/5000 (1 + 1/5002) = 25009997/25010000 < 1, and the last tangent 1036/2501 is past tan(pi/8), every unit square contains a concentric core at a net angle strictly in its interior.

The source reports every such core capturing mass at least one at all 2,073 directions, by sqverify-proof-net, its copy of this repository's sqverify_fast changed to read the declared net, in two complete runs, and a control with every mass scaled by 197/200 refused at 32 sampled directions.

The value is above T-090's 747/100 = 7.47, the verified and reported lower bound at n=51, by 23/400.

Here the maintained readers accepted its exact mass, declared-net and check2 premises from the retained release asset. No complete replay has run here, so the value stands as reported.

wand125 after Tokoharu and Levy, square-packing. The source says parts of the work were produced with AI assistance under human direction.

Significance, composition and next rung
Significance
Scored as a claim: if a complete replay passes, it is the strongest lower bound on record at n=51, 23/400 above the reported lane, by the certificate kind and declared net of T-132, T-142 and T-143, with no new technique, at S3 as T-176 to T-178 are.
Composition
One reported certificate on its reported entry. The source's check is a copy of this repository's sqverify_fast crate with one change, so a sqverify-fast replay here would be re-implemented sharing the producer's components, as T-104's is, and no second implementation stands beside it.
Next rung
C3 needs a complete sqverify-fast census at all 2,073 directions of the retained candidate, with its whole-net control receipt (the 99/100 mutant at every direction, FC-1) and a review that reads this certificate, by the checklist of the 6 October declared-net soundness review. The census runs in think-f40c, priced at about 13.84 to 15.89 CPU-hours from the source's receipt.
Unfinished confirmations
C3 (think-f40c): a complete sqverify-fast census at all 2,073 directions of the retained candidate, with its whole-net control receipt (the 99/100 mutant at every direction, FC-1) and a review that reads this certificate, by the checklist of the 6 October declared-net soundness review. About 13.84 CPU-hours, up to about 15.89 (priced 2026-10-17).
Novelty
previously-published Present in an identified source

The case

Case record

n=51

7.477.690
789
7.1418.141
nn+1

Proven

7.47000≤s(51)≤7.690356

  • exact

Citation record n-051

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

upperXu 2026, GitHub (confirmed T-126)

Open

  • optimality

The case record

LowerUpper
Gap523−641300≈ 0.22035593…

Results on the case

14 results in the register on n=51, oldest first, each with what it established and how it stands now.

  1. 2005 published T-007

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

    V0 C1 Lower bound incomplete on this case, superseded by T-090

    Nagamochi · Nagamochi 2005 · source · register

  2. 2026-09-04 published T-085

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

    V3 C3 Correction confirmed

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

  3. 2026-09-27 published T-046

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

    V0 C0 Lower bound recorded superseded by T-090

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

  4. 2026-09-28 published T-048

    s(50)≥37/5=7.4

    V3 C3 Lower bound confirmed on this case, superseded by T-090

    Hosono after Daniel, Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 point and mixed bounds 2026-09-28 · packet · source · review · register

  5. 2026-09-28 published T-070

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

    V3 C3 Lower bound confirmed superseded by T-090

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

  6. 2026-09-29 published T-058

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

    V3 C3 Method limit confirmed

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

  7. 2026-09-29 published T-083

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

    V3 C3 Lower bound confirmed on this case, superseded by T-090

    Karakuş · Karakuş 2026 · source · register

  8. 2026-10-03 published T-082

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

    V3 C3 Lower bound confirmed on this case, superseded by T-090

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

  9. 2026-10-04 published T-090

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

    V3 C3 Lower bound confirmed

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

  10. 2026-10-05 published T-101

    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 this case, superseded by T-126

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

  11. 2026-10-08 published T-125

    Complete rational construction reports at 25 counts

    V3 C3 Upper bound confirmed superseded by T-126

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

  12. 2026-10-08 published T-126

    Undilated n51 construction over Q(sqrt2)

    V3 C3 Upper bound confirmed

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

  13. 2026-10-13 published T-180

    Closed-form lower bound s(N)≥a(N) for every non-square N≥49, reported

    V0 C1 Lower bound reviewed on this case, superseded by T-090

    Hosono · wand125 closed form 2026-10-14 · packet · packet · register

  14. 2026-10-16 published T-204 this result

    Mixed rectangle-measure lower bound s(51)≥3011/400 reported, on a 2,073-direction declared net

    V0 C0 Lower bound recorded

    Hosono after Tokoharu and Levy · wand125 fine-net lower bounds 2026-10-16 · packet · register