T-222: Daniel's smaller n154 packing, continuing Couzo's #586 arrangement, certified exactly

V3 C3 Upper bound confirmed

2026-10-20 published · Daniel after Couzo, Ostashev, Levy · n=154

One complete rational source certificate reports a finite upper-bound improvement at the exact side it states: s(154)≤12.921100940761680549856582087576.

The certificate and its duplicate-square and outside-container controls were decided here on 20 October 2026 by both maintained exact routes, and the frozen comparison rebuilt; no route here is the source's code, so the replay is independently re-implemented. The 20 October review found no blocking defect.

Issue 694 reports a packing found by Daniel's chained explorer, which removed two squares from the register's s(156) packing (Ostashev's), and by crossovers against close relatives of Couzo's #586 packing and a later restart of his basin explorer; it asks that #586's arrangement (itself continued from Daniel's #552) and Ostashev's s(156) packing be credited as its starts, and calls it a different KKT point from #586's in the same family. Measured here pose by pose, the packing is #586's arrangement continued, three squares beyond a tenth; Ostashev's packing is not near it by pose, so his credit as the search's start rests on the source's account of the search, and Couzo's on the measured arrangement.

The author reports that his two exact checkers accept the certificate and its 10-group regularized view at the same side, and a KKT point that his second-order test leaves inconclusive, with 58 corner-corner contacts, no corner-corner MILP descent, 9 rattlers and 38 tilted squares; those are numerical evidence at 80 digits, not proofs. The source's credits say the work was done with Claude (Anthropic) under Daniel's direction.

Significance, composition and next rung
Significance
#586's arrangement continued to a new KKT point 1.06e-04 below the case, three squares beyond a tenth, as T-219 at 271 and T-172's 6.66e-05 at this count are; no lower bound or optimum, and the source's inconclusive second-order status bears on the minimum, not on the bound.
Next rung
None for the bound. V4 and C4 need a second accepted adversarial review by a distinct reviewer and a retained human oversight record; one AI review, of 20 October, is retained.
Regularized drawings
n = 154: a regularization of T-222’s packing by Levy (Daniel's search/regularize (MIT), evand/square-packing@675a5ea, conservative, coincide, through devtools.regularize_evand; the project’s modifications: same-side exact re-solve (devtools.regularize_same_side); at its own side; 4 free squares straightened, 5 free angles moved; identity: measured here; nearest centres one to one; 47 squares moved, at most 0.0779303; turns up to 0.851377°).
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, Daniel 2026 [Daniel n154 sweep 2026-10-20]

n=154

12.4212.921
121314
12.41013.410
nn+1

Proven

12.42686≤s(154)≤12.921101

  • exact

Citation record n-154

lowerKarakuş 2026, arXiv corrects Nagamochi 2005 (confirmed T-083)

upperDaniel & Couzo, GitHub (confirmed T-222)

Open

  • optimality

The case record

LowerUpper
Gap0.49424049…

Results on the case

15 results in the register on n=154, 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-083 and T-180 (reported)

    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-056

    Smaller packings for 49 counts from n=68 to 307, each certified two independent ways

    V3 C3 Upper bound confirmed superseded by T-222

    Couzo · franciscouzo square-packing 2026-09-27 · packet · register

  4. 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

    Karakuş · Karakuş 2026 · source · register

  5. 2026-10-05 published T-098

    Exact optima of 48 known-best packings: s(n) ≤ S', 3.5e-13 to 5.0e-11 below each printed side

    V3 C3 Upper bound confirmed on this case, superseded by T-222

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

  6. 2026-10-07 published T-113

    s(n)≤Sn at ten counts, n=108 to 303, from new SQUISH rational packings

    V3 C3 Upper bound confirmed superseded by T-222

    Chaoweeraprasit after Ellsworth · SQUISH ten packings 2026-10-07 · packet · register

  7. 2026-10-07 published T-115

    s(n)≤Sn at twelve counts, from the SQUISH update’s new and smaller rational packings

    V3 C3 Upper bound confirmed superseded by T-222

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

  8. 2026-10-08 published T-127

    Fourteen rational refinements, seventeen complete source cases

    V3 C3 Upper bound confirmed on this case, superseded by T-222

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

  9. 2026-10-09 published T-136

    Seventeen exact rational packings from SQUISH's third request

    V3 C3 Upper bound confirmed on this case, superseded by T-222

    Chaoweeraprasit after Couzo, Xu, Göbel, Schadt, Ellsworth, Hajba, Levy · SQUISH third request 2026-10-09 · packet · register

  10. 2026-10-12 published T-160

    A smaller packing of 154 squares from Daniel's size-chaining explorer, certified exactly

    V3 C3 Upper bound confirmed superseded by T-222

    Daniel after Couzo, Levy · Daniel n154 2026-10-12 · packet · register

  11. 2026-10-12 published T-172

    A packing of 154 squares from Couzo, continuing Daniel's arrangement

    V3 C3 Upper bound confirmed superseded by T-222

    Couzo after Daniel, Ostashev, Fang, Ellsworth, Levy · Couzo issue-583 certificates 2026-10-13 · packet · register

  12. 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

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

  13. 2026-10-13 published T-182

    Exact rational certificates at 154, 211 and 241 from Couzo

    V3 C3 Upper bound confirmed on this case, superseded by T-222

    Couzo after Daniel, Ostashev, BuddenPing, Fang, Ellsworth, Levy · Couzo certificates 2026-10-13 · packet · register

  14. 2026-10-14 published T-186

    Exact certificates at twelve counts from Polkovskyi, tightening the smallest reported there

    V3 C3 Upper bound confirmed on this case, superseded by T-222

    Polkovskyi after Ostashev, Couzo, PingYou Ltd, Levy · Mishapolk KKT refinements 2026-10-14 · packet · register

  15. 2026-10-20 published T-222 this result

    Daniel's smaller n154 packing, continuing Couzo's #586 arrangement, certified exactly

    V3 C3 Upper bound confirmed

    Daniel after Couzo, Ostashev, Levy · Daniel n154 sweep 2026-10-20 · packet · packet · register