T-071: Mixed rectangle-measure lower bounds replayed at n=84…87

V3 C3 Lower bound confirmed superseded by T-090, T-091, T-206 and T-207

2026-10-02 published · Hosono after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · n=84,85,86,87

Two rectangle densities of wand125/square-packing-bounds, checked at coverage one and published on 2 October 2026, prove s(84)≥47/5 = 9.4 and s(85)≥471/50 = 9.42. The n=85 certificate's mass is below 86 and 87 too, so it gives s(86)≥471/50 and s(87)≥471/50 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 n=84 and 587 at n=85. 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 s(50) 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 n=84 and 1.0000000017 at n=85.

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 n=82, 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 n=86 and 87 the n=85 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.

Hosono 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.

Significance, composition and next rung
Significance
Raised the verified lower bound at four counts, n=84 to 87, past Green's reported value at n=84 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.
Composition
Two primary certificates, each on its own reported entry and its own replay entry. n=86 and 87 take the n=85 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 n=37 certificate of the same kind.
Novelty
previously-published Present in an identified source

The cases

Case record

n=84

9.429.698
91011
9.16510.165
nn+1

Proven

9.42250≤s(84)≤9.697935

  • exact

Citation record n-084

lowerHosono after Tokoharu and Levy 2026, GitHub (confirmed T-206)

upperXu et al., GitHub (confirmed T-174)

Open

  • optimality

The case record

LowerUpper
Gap0.27543479…
Case record
Regularized by the Squares Project with Daniel's regularizer (evand/square-packing, MIT)
As published
The packing as published, Friedman 1997 [Kingbird]

n=85

9.479.743
91011
9.22010.220
nn+1

Proven

9.47500≤s(85)≤9.742641

  • exact

Citation record n-085

lowerHosono after Tokoharu and Levy 2026, GitHub (confirmed T-207)

upperFriedman 1997, Squares in Squares

Open

  • optimality

The case record

LowerUpper
Gap32−15940≈ 0.26764068…
Case record

n=86

9.509.821
91011
9.27410.274
nn+1

Proven

9.50300≤s(86)≤9.820536

  • exact

Citation record n-086

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

upperXu et al., GitHub (confirmed T-174)

Open

  • optimality

The case record

Case record
Regularized by the Squares Project with Daniel's regularizer (evand/square-packing, MIT)
As published
The packing as published, Ellsworth 2024 [Kingbird]

n=87

9.589.839
91011
9.32710.327
nn+1

Proven

9.58000≤s(87)≤9.838816

  • exact

Citation record n-087

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

upperEllsworth et al., Squares in Squares (confirmed T-101, T-155)

Open

  • optimality

The case record

LowerUpper
Gap0.25881526…

Results on these cases

24 results in the register on n=84,85,86,87, oldest first, each with what it established and how it stands now.

  1. 2005 published T-007 · n=84,85,86,87

    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, T-206 and T-207

    Nagamochi · Nagamochi 2005 · source · register

  2. 2026-09-04 published T-085 · n=84,85,86,87

    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. 2026-09-24 published T-089 · n=87

    s(83)≤9.63475764863195 and s(87)≤9.83881526994915, Chang's packings, certified exactly

    V3 C3 Upper bound confirmed superseded by T-101 and T-155

    Chang, Ellsworth after Cantrell, Hajba, Stenlund, Bidwell; Chang after Ellsworth, Cantrell, Schadt, Hajba, DeVincentis · Chang n83 2026-09-24 · Chang n87 2026-09-24 · packet · packet · register

  4. 2026-09-27 published T-046 · n=86

    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

  5. 2026-09-28 published T-070 · n=86

    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 · n=84,85,86,87

    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 · n=84,85,86,87

    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, T-206 and T-207

    Karakuş · Karakuş 2026 · source · register

  8. 2026-10-01 published T-068 · n=86,87

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

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

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

  9. 2026-10-02 published T-071 this result · n=84,85,86,87

    Mixed rectangle-measure lower bounds replayed at n=84…87

    V3 C3 Lower bound confirmed superseded by T-090, T-091, T-206 and T-207

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

  10. 2026-10-02 published T-075 · n=85,86,87

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

    V3 C3 Lower bound confirmed on these cases, superseded by T-090, T-091 and T-207

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

  11. 2026-10-03 published T-082 · n=86,87

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

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

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

  12. 2026-10-04 published T-090 · n=84,86

    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

  13. 2026-10-04 published T-091 · n=87

    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

  14. 2026-10-05 published T-094 · n=84

    Mixed rectangle-measure lower bounds verified at n=67 and 84

    V3 C3 Lower bound confirmed on these cases, superseded by T-206

    Hosono after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 mixed bounds 2026-10-05 · packet · source · review · register

  15. 2026-10-05 published T-101 · n=87

    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

  16. 2026-10-08 published T-125 · n=84,86

    Complete rational construction reports at 25 counts

    V3 C3 Upper bound confirmed superseded by T-174

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

  17. 2026-10-08 published T-130 · n=84,86

    Five follow-up rational refinements from Couzo

    V3 C3 Upper bound confirmed superseded by T-174

    Couzo after Xu, Daniel, Ellsworth, Levy · Couzo follow-up refinements 2026-10-08 · packet · register

  18. 2026-10-09 published T-138 · n=84,86

    Exact witnesses at Mishapolk's printed ceilings, the smallest known at 103 and 258 when registered

    V3 C3 Upper bound confirmed superseded by T-174

    Polkovskyi after Stenlund, Friedman, Ellsworth, Chaoweeraprasit, Couzo, Xu, Levy · Mishapolk decimal poses 2026-10-09 · packet · register

  19. 2026-10-12 established T-155 · n=87

    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

  20. 2026-10-13 published T-174 · n=84,86

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

    V3 C3 Upper bound confirmed

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

  21. 2026-10-13 published T-180 · n=84,85,86,87

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

    V0 C1 Lower bound reviewed on these cases, superseded by T-090, T-091, T-206 and T-207

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

  22. 2026-10-16 published T-206 · n=84

    Mixed rectangle-measure lower bound s(84)≥3769/400 verified, on the 201-direction net

    V3 C3 Lower bound confirmed

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

  23. 2026-10-16 published T-207 · n=85

    Mixed rectangle-measure lower bound s(85)≥379/40 verified, on the 201-direction net

    V3 C3 Lower bound confirmed

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

  24. 2026-10-16 published T-208 · n=86

    Mixed rectangle-measure lower bound s(86)≥3811/400 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