T-176: Mixed rectangle-measure lower bound s(39)≥533/80 reported, on a 2,073-direction declared net

V0 C1 Lower bound reviewed

2026-10-13 published · Hosono after Tokoharu and Levy · n=39

A rectangle measure of wand125/square-packing, published on 13 October 2026 and reported on no issue, is reported to prove s(39)≥533/80 = 6.6625.

The certificate, mixed_n39_L66625, is a density of 687 uniform rectangles in D4 orbits, and no point mass, of total mass 3899999/100000, 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-110's 133/20 = 6.65, the verified and reported lower bound at n=39, by 1/80.

Here the maintained readers accepted its exact mass, declared-net and check2 premises, and sqverify-fast, this repository's clean-room measure verifier, verified it at eight sampled directions with the source's node counts and least certified bounds: a diagnostic, not a replay. No complete replay has run here, so the value stands as reported.

Hosono 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=39, 1/80 above T-110, by the certificate kind and declared net of T-132, T-142 and T-143, with no new technique, at S3 as they 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 run at all 2,073 directions from a 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 eight-direction sample prices the run and its controls at about 7.1 CPU-hours. The control cannot pass as the census stands: at the axis direction the 99/100 mutant's exact capture sits 1.26e-9 above the vertex sweep's certified bound, beyond AXIS_ROUNDING (1e-9), the defect T-142's control is held for. The run waits for an owner budget, a decision on that tolerance and the candidate's retention where the census reads it (jlevy/squares#543), in think-u0av.
Unfinished confirmations
C3 (think-u0av): a complete sqverify-fast census at all 2,073 directions from a 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 7.09 CPU-hours, up to about 7.5 (priced 2026-10-14).
Novelty
previously-published Present in an identified source

The case

Case record

n=39

6.656.811
678
6.2457.245
nn+1

Proven

6.65000≤s(39)≤6.810723

  • exact

Citation record n-039

lowerHosono after Tokoharu, Levy et al. 2026, GitHub (confirmed T-110)

upperSchadt 2026, Squares in Squares (confirmed T-101, T-155)

Open

  • optimality

The case record

LowerUpper
Gap0.16072208…

Results on the case

13 results in the register on n=39, 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-110

    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. 2026-09-22 published T-044

    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-110

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

  4. 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-110

    Hosono after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026 · wand125 rectangle bounds 2026-09-28 · packet · packet · 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-110

    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-110

    Karakuş · Karakuş 2026 · source · register

  8. 2026-10-01 published T-068

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

    V3 C3 Lower bound confirmed on this case, superseded by T-110

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

  9. 2026-10-01 published T-074

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

    V3 C3 Lower bound confirmed on this case, superseded by T-110

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

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

  11. 2026-10-06 published T-110

    Mixed rectangle-measure lower bound verified at n=39, on a declared net

    V3 C3 Lower bound confirmed

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

  12. 2026-10-12 established T-155

    Exact regularized sides at 59 counts, 5.4e-20 to 9.9e-15 below the ceilings they replace

    V3 C3 Upper bound confirmed

    Levy after Daniel · register

  13. 2026-10-13 published T-176 this result

    Mixed rectangle-measure lower bound s(39)≥533/80 reported, on a 2,073-direction declared net

    V0 C1 Lower bound reviewed

    Hosono after Tokoharu and Levy · wand125 fine-net n37 n39 n44 2026-10-13 · packet · register