T-088: s(69)≤8.82719465572975, Ellsworth's degree-38 packing, certified exactly from its picture

V3 C3 upper bound confirmed superseded by T-101

2026-09-24 published · Ellsworth after hmbelvedere, Cantrell, Schadt, Morandi · n=69

s(69)≤8.82719465572975, by David Ellsworth's packing of 69 unit squares, certified here exactly. The Kingbird catalogue prints the packing's side as 8.82719465572973, cut short from 8.827194655729738914..., the root near it of the degree-38 polynomial the catalogue prints; neither of those two is certified here.

In the catalogue's words, the packing was "Refound by David Ellsworth in September 2026, using his modified version of Thomas Schadt's simulated annealing program, starting from s(69) found by Maurizio Morandi in June 2010", and "Optimized by David Ellsworth in September 2026". It is the packing whose side hmbelvedere's UnitSquare release reported in July 2026 as 8.8272055078..., which the catalogue lists as "Improved by hmbelvedere in July 2026, using an undisclosed iterative method (probably with AI)", after David W. Cantrell's improvement of August 2023; the optimization lowers that side by about 1.1e-5.

The catalogue states no checker, and its picture, which holds the pose, could not be fetched. The certificate is a third party's binary64 parse of that picture, rounded to rationals and dilated about its centre by 1 + 1e-15: an exact rational packing of side 8.8271946557297478..., 1.8e-14 above the printed side, decided pair by pair and wall by wall over Q by two checkers of this repository that share no geometry or verification code, and refused by both when its side is cut by 1e-15 or one square is moved by 1e-6. The bound above is that side rounded up at the printed precision.

David Ellsworth, September 2026, in the Squares in Squares catalogue.

Significance, composition and next rung
Significance
Lowers the best known side at one count by about 1.1e-5, by optimizing a packing already reported. S2 by the anchor "a citable detail that changes no theorem".
Next rung
V4 and C4 need two adversarial AI reviews by distinct reviewers of the claim and a human oversight record; the review of 2026-10-05 is one. The verified bound sat 2e-14 above the printed side because the certificate is a binary64 parse; the pose refined on its active contacts, Evan Daniel's exact certificate (T-101), has since brought the case's verified upper bound within one unit of the printed side's last place. A method-distinct second route is what C4 needs.
Novelty
previously-published Present in an identified source

The case

Case record

n=69

8.628.827
8910
8.3079.307
nn+1

Proven

8.62000≤s(69)≤8.827195

  • exact

Citation record n-069

lowerwand125 after Tokoharu, Levy et al. 2026, GitHub (confirmed T-090)

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

Open

  • optimality

The case record

LowerUpper
Gap0.20719465…

Results on the case

13 results in the register on n=69, 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; chelokot · 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-090

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

  4. 2026-09-24 published T-088 this result

    s(69)≤8.82719465572975, Ellsworth's degree-38 packing, certified exactly from its picture

    V3 C3 upper bound confirmed superseded by T-101

    Ellsworth after hmbelvedere, Cantrell, Schadt, Morandi · Ellsworth n69 2026-09-24 · packet · packet · register

  5. 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

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

  6. 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

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

  7. 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

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

  8. 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

  9. 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-090

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

  10. 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-090

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

  11. 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

    wand125 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

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

    V3 C3 lower bound confirmed

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

  13. 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