T-087: s(37)≥53/2+22−1 and s(61)≥73/2+22−1, by optimal piercing

V3 C1 lower bound reviewed superseded by T-063 and T-069

2018 published · Bašić, Slivková · n=37,61

Bašić and Slivková 2018, Theorem 7 with Proposition 8: no more than B(x) unit squares fit in a square of side x, where B(x) counts the points of an equilateral-lattice piercing set, floor(x)(m + 2) plus floor((m + 2)/2) when frac(x) >= 1/2, with m = floor((2/sqrt 3)(x + 1 - 2 sqrt 2)). Just below 7 sqrt(3)/2 + 2 sqrt(2) - 1 it is 60, so s(61)≥7 sqrt(3)/2 + 2 sqrt(2) - 1, about 7.8906 (their Theorem 10); just below 5 sqrt(3)/2 + 2 sqrt(2) - 1 it is 36, so s(37)≥5 sqrt(3)/2 + 2 sqrt(2) - 1, about 6.1586, which the paper does not state.

Both are above Karakuş's general floor, T-083; at every other case the theorem is weaker than the verified floor already held. The proof uses nothing of Nagamochi 2005. It was read and re-derived here and is not machine-checked; its arithmetic is replayed exactly for every case by devtools/check_piercing_lower_bounds.py. Bašić and Slivková, Discrete Applied Mathematics 247 (2018).

Significance, composition and next rung
Significance
Registered as the verified lower bound at n=37 and n=61, the only two cases where the piercing bound beat the floor its line of the register held; the merge of 3 October 2026 brought stronger replayed bounds to both, so it holds neither now. S3 by the anchor "a substantive case result or machine audit"; the score is the theorem's, not ours.
Next rung
C2 and above need a replay of the geometry, not only the arithmetic: a machine check that the lattice of Theorem 7 pierces every unit square in the square of side x, or a formalization of the three-case reduction in Theorem 3's proof.
Unfinished confirmations
C2: a replay of the geometry: a machine check that the lattice of Theorem 7 pierces every unit square in the square of side x, or a formalization of the three-case reduction in Theorem 3's proof. Not priced.
Novelty
previously-published Present in an identified source

The cases

Case record

n=37

6.446.599
678
6.0837.083
nn+1

Proven

6.44000≤s(37)≤6.598620

  • exact

Citation record n-037

lowerwand125 after Tokoharu, Levy et al. 2026, GitHub (confirmed T-069)

upperCantrell 2002, Squares in Squares (confirmed T-101)

Open

  • optimality

The case record

LowerUpper
Gap0.15861960…
Case record

n=61

8
789
7.8108.810
nn+1

Proven

s(61)=8

  • optimal
  • exact

Citation record n-061

lowerDaniel after Burns, Massaccesi 2026, GitHub (confirmed T-063)

The case record

LowerUpper
Verified88
Reported88
Gap0 solved: the verified bounds meet

Results on these cases

12 results in the register on n=37,61, oldest first, each with what it established and how it stands now.

  1. 2005 published T-007 · n=37,61

    s(n)≥min(⌈n⌉,n−2⌊n⌋+1+1) for 4≤n≤324

    V0 C1 lower bound incomplete on these cases, superseded by T-063 and T-069

    Nagamochi · Nagamochi 2005 · source · register

  2. 2018 published T-087 this result · n=37,61

    s(37)≥53/2+22−1 and s(61)≥73/2+22−1, by optimal piercing

    V3 C1 lower bound reviewed superseded by T-063 and T-069

    Bašić, Slivková · Basic-Slivkova 2018 · source · register

  3. 2026-09-04 published T-085 · n=37,61

    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

  4. 2026-09-27 published T-045 · n=61

    Rectangle-density lower bounds replayed at 15 counts in n=18…78

    V3 C3 lower bound confirmed superseded by T-063

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

  5. 2026-09-27 published T-046 · n=37,61

    Rectangle-density lower bounds reported for 48 counts in n=18…95

    V0 C0 lower bound recorded superseded by T-063 and T-069

    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-063 · n=61

    s(61)=8, by monotonicity from T-062

    V3 C3 optimality confirmed

    Daniel after Burns, Massaccesi · evand square-packing 2026-10-01 · packet · packet · packet · source 1 · source 2 · review 1 · review 2 · register

  7. 2026-09-29 published T-058 · n=37,61

    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 · n=37,61

    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-063 and T-069

    Karakuş · Karakuş 2026 · source · register

  9. 2026-09-30 published T-064 · n=61

    s(k2−3)=k for every integer k from 6 up; k=6…18 are the cases held here

    V3 C3 optimality confirmed on these cases, second certificate

    Daniel after Burns, Massaccesi · evand square-packing 2026-10-01 · packet · packet · packet · packet · source 1 · source 2 · review 1 · review 2 · register

  10. 2026-10-01 published T-069 · n=37

    Mixed rectangle-measure lower bounds replayed at n=37,65,66,90,92

    V3 C3 lower bound confirmed

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

  11. 2026-10-05 published T-101 · n=37

    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

  12. 2026-10-07 published T-124 · n=61

    Reported non-strict local minima for 178 source configurations

    V0 C0 restricted optimality recorded

    Daniel after Couzo · Daniel exact and local reports 2026 · packet · register