n = 82 open ★=

23325≤s(82)≤6+522

The best packing known for 82 squares, side 6+522, Frits Göbel 1979
9.3209.536
91011
9.05510.055
nn+1

Proven

9.320000≤s(82)≤9.535534

  • new result
  • exact

Citation record n-082

lowerwand125 after Tokoharu, Levy et al. 2026, GitHub (confirmed T-076)

upperGöbel 1979, Squares in Squares

Open

  • optimality

Bounds

Best known packing

6+522

9.53553390593273
Found by
Frits Göbel 1979
Construction
hand
Source
[Kingbird]
Evidence
E-kingbird-upper-register, E-n082-gobel-l-upper
Verified upper bound

6+522

9.53553390593273762200422181052425

The reported value, verified here.

Evidence
E-n082-gobel-l-upper
Reported lower bound

23325

Proved by
wand125 2026
Kind
counting
Scope
Unrestricted unit-square packing with independent rotations and disjoint interiors.
Note
wand125's square-packing-bounds (2 October 2026) reports s(82)≥233/25 from a measure of 86 point, 222 segment and 774 rectangle orbits of total mass 8199999/100000, at core side 9977/10000 on 201 net half-angles, accepted there at every angle by its linear verifier, code/unified_linear_verify.cpp. It is above Green's reported 9.2667335..., which this case reported before it, and does not rest on Green's argument. Its complete replay here on 3 October 2026 matched the source's run at all 201 directions.
Source
[wand125 linear n82 2026-10-02]
Evidence
E-n082-wand125-linear-932-report
Verified lower bound

23325

The reported value, verified here.

Evidence
E-n082-wand125-linear-932-source-replay
Gap

522−8325≈ 0.21553390…

Verified upper minus verified lower.

Results in the register

Verification

upper: replayed here; lower: replayed here

—

Rigidity

not rigid, numerically checked, numerical multiprecision

Evidence: E-translation-escape-not-rigid

Scope

Square 33 of the retained witness (witness id 34) translates 0.535534 along (1, 0) with the packing still valid, so the configuration admits a non-trivial feasible motion; 8 of its 82 squares do. Every constraint is exactly affine in the slide parameter, so the arithmetic carries no linearization error, but the coordinates are the witness's own finite-precision transcription: this settles the retained configuration, not the true optimum. Rigidity and optimality are independent, and this bears only on the former.

Open questions
  • Blocker (source evidence): Green's reported lower-bound proof, cited as private communication by Friedman, has not been recovered or independently replayed. E-green-ds7-theorem9-reported-lower

s(82) — open

External intake, 2026-10-02 (afternoon). wand125’s linear-certificate source reports s(82)≥233/25=9.32 (T-076), from a measure of points, segments and rectangles of total mass 8199999/100000<82 on the support of its n=83 linear certificate scaled by 932/935, accepted there at every net angle by the linear verifier the 2 October reviews read with no blocking defect. It is above Green’s reported 9.2667335…, the value this case reported before it, by 0.0532664…, and does not rest on Green’s argument, which jlevy/squares#308 reports the published material does not establish for k≥4. Its complete replay here on 3 October 2026 returned the certificate’s own record at all 201 directions, so it is also the verified lower bound. wand125’s README says parts of the work were produced with AI assistance under human direction.

Open. The best known packing gives s(82)≤9.53553391, and the verified lower bound is s(82)≥233/25=9.32, from wand125’s linear certificate, leaving a gap of 0.2155.

The packing

Found by Frits Göbel in 1979, via a hand construction: the n=65 centred-block family pose with one L of seventeen unit squares around it, exactly as [Friedman DS7] section 2 states. cases/gobel82 builds it and verifies it exactly over Q(sqrt 2), which is what moved verified_upper_bound from the grid ceiling onto 6+(5/2)2. The retained witness declares that side — the exact value correctly rounded up at its thirty-two digits — but a different layout: its centre set matches none of the construction’s eight dihedral images, so the certificate is about the construction, not the witness’s drawing.

The lower bound

Before wand125’s certificate above, the selected external report was [Friedman DS7], which gives the lower-bound expression 942/41+247/41 for s(82) (approximately 9.266733533246). Friedman’s DS7 survey, Theorem 9, k=9, reports this bound at n=82; reference [8] is Green’s private communication (2000). The source proof has not been recovered. The unavoidable-set argument DS7’s Figure 34 illustrates does not prove it: at k=9 that point pattern leaves a unit square empty (review). That changed the reported source field only; the verified field now holds wand125’s replayed linear certificate. The source audit compares the exact theorem expressions separately from opaque table decimals.

The verified field rests on a complete replay here (E-n082-wand125-linear-932-source-replay, V3/C3) of wand125’s linear certificate: the source’s unchanged checker and replay functions on the pinned bundle, all 201 directions on 3 October 2026, each returning the certificate’s own record. It runs the source’s own algorithm, so it confirms the source’s run rather than deciding coverage a second way.

Until 2 October 2026 the verified lower bound was Nagamochi’s general closed form, now a reported bound (see the correction below), and from then until this replay it was Karakuş’s general bound, which applies to every nonsquare N≥8:

s(N)≥12+N−⌊N⌋+14

Correction, 2 October 2026. Until that date the verified lower bound here was Nagamochi’s general closed form, s(N)≥min(⌈N⌉,N−2⌊N⌋+1+1), which is stronger at this n and is now recorded as a reported bound. Its published proof rests on Nagamochi’s Lemma 1, which Karakuş showed false; nothing is disproved, and no packing beating it is known (review of 2 October 2026). This register had recorded that proof as verified, its own error, logged as defect D-516.

See the Frontier corpus summary for the current aggregate count; source-reported bounds are recorded separately.

Verification Code

The programs behind this case’s verified bounds, by their evidence. The code column says how the code that ran stands to the code its producer used. VERIFIERS.md says what each program is and whose it is.

bound evidence run code programs
verified lower E-n082-wand125-linear-932-source-replay replayed here producer’s code V-wand125-unified-linear-verify-cpp (external); V-audit-wand125-linear (first-party, premises)
verified upper E-n082-gobel-l-upper replayed here independent V-sqpack-verify (first-party)