T-209: Mixed rectangle-measure lower bound s(88)≥3853/400 reported, on the 201-direction net

V0 C0 Lower bound recorded

2026-10-16 published · Hosono after Tokoharu and Levy · n=88

A rectangle measure of wand125/square-packing, published on 16 October 2026 and reported in jlevy/squares#446, is reported to prove s(88)≥3853/400 = 9.6325.

The certificate, mixed_n88_L96325, is a density of 754 uniform rectangles in D4 orbits, and no point mass, of total mass 8799999/100000, on the net its candidate declares, the standard net of 201 half-angle tangents of step 83/40000 at core side 9977/10000. Since 9977/10000 (1 + 83/40000) = 399908091/400000000 < 1, and the last tangent 83/200 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 201 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-091's 481/50 = 9.62, the verified and reported lower bound at n=88, by 1/80.

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=88, 1/80 above the reported lane, by the certificate kind and standard net of T-082, T-090 and T-091, 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 201 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 1.88 to 2.16 CPU-hours from the source's receipt.
Unfinished confirmations
C3 (think-f40c): a complete sqverify-fast census at all 201 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 1.88 CPU-hours, up to about 2.16 (priced 2026-10-17).
Novelty
previously-published Present in an identified source

The case

Case record
Regularized by the Squares Project with Daniel's regularizer (evand/square-packing, MIT)
As published
The packing as published, Chaoweeraprasit 2026 [Gupta rational refinements 2026-10-08]

n=88

9.629.882
91011
9.38110.381
nn+1

Proven

9.62000≤s(88)≤9.882452

  • exact

Citation record n-088

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

upperChaoweeraprasit & Gupta, GitHub (confirmed T-127)

Open

  • optimality

The case record

LowerUpper
Gap0.26245103…

Results on the case

19 results in the register on n=88, 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-091

    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-091

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

  4. 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

  5. 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-091

    Karakuş · Karakuş 2026 · source · register

  6. 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-091

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

  7. 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-091

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

  8. 2026-10-02 published T-075

    Mixed rectangle-measure lower bounds replayed at nine counts in n=83…96

    V3 C3 Lower bound confirmed on this case, superseded by T-091

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

  9. 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-091

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

  10. 2026-10-04 published T-090

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

    V3 C3 Lower bound confirmed on this case, superseded by T-091

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

  11. 2026-10-04 published T-091

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

    V3 C3 Lower bound confirmed

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

  12. 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-127

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

  13. 2026-10-07 published T-116

    s(n)≤Sn at nine counts, from the second SQUISH update’s new rational packings

    V3 C3 Upper bound confirmed superseded by T-127

    Chaoweeraprasit after Ellsworth, Couzo and SQUISH · SQUISH second update 2026-10-07 · packet · register

  14. 2026-10-08 published T-125

    Complete rational construction reports at 25 counts

    V3 C3 Upper bound confirmed superseded by T-127

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

  15. 2026-10-08 published T-127

    Fourteen rational refinements, seventeen complete source cases

    V3 C3 Upper bound confirmed

    Gupta after Chaoweeraprasit, Daniel · Gupta rational refinements 2026-10-08 · packet · register

  16. 2026-10-13 published T-174

    Tighter certificates at 68 counts from PingYou Ltd, of others' packings and its own

    V3 C3 Upper bound confirmed on this case, superseded by T-127

    PingYou Ltd after Friedman, Ellsworth, Daniel, Xu, Barnett, Couzo, Ostashev, Chaoweeraprasit, Gupta, Fang, Polkovskyi, Levy · PingYou PR 574 certificates 2026-10-13 · packet · register

  17. 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-091

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

  18. 2026-10-16 published T-193

    Exact algebraic sides at sixteen counts from Daniel, of packings the record credits

    V3 C3 Upper bound confirmed

    Daniel after Xu, Chaoweeraprasit, Ostashev, Couzo, PingYou Ltd, Gupta, Polkovskyi, Levy · Daniel exact current records 2026-10-16 · packet · register

  19. 2026-10-16 published T-209 this result

    Mixed rectangle-measure lower bound s(88)≥3853/400 reported, on the 201-direction net

    V0 C0 Lower bound recorded

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