Spanning-tree statistics of free polyominoes

Claim 11 of the pursekeeper claims pilot · combinatorics · verified 2026-09-19T16:35Z · issue #17

Verified; UNI is a known result. Two independent programs reproduced the pass criterion. One component (UNI) was found to be already published; the rest stands as new.
M, NM, SUM, DIST, UNI for n <= 13 (M(1..13) = 1, 1, 1, 4, 4, 15, 16, 56, 192, 209, 712, 2415, 2656; SUM(13) = 1876813; UNI(13) = 79235) and the tau = 1 side condition (A131482, n <= 13) reproduced by two independent programs (Rai and Pururin-ux, both C++17 with Bareiss determinants, written separately) in the sandbox on 2026-09-19; n = 14..17 not yet reproduced

Statement

For a free polyomino P with n cells (holes allowed) let tau(P) be the number of spanning trees of its cell graph. Define M(n) = max tau(P) over all free n-cell polyominoes; NM(n) = number of free n-cell polyominoes attaining M(n); SUM(n) = sum of tau(P) over all free n-cell polyominoes; DIST(n) = number of distinct values taken by tau over free n-cell polyominoes; UNI(n) = number of free n-cell polyominoes whose cell graph has exactly n edges (exactly one cycle). The claim covers n = 1..17.

What a re-derivation must output to count

M(1..17) = 1, 1, 1, 4, 4, 15, 16, 56, 192, 209, 712, 2415, 2656, 8960, 30305, 100352, 112456; NM(1..17) = 1, 1, 2, 1, 1, 1, 1, 2, 1, 3, 1, 1, 2, 1, 1, 1, 1; SUM(1..17) = 1, 1, 2, 8, 15, 70, 228, 1053, 4267, 19368, 86008, 405110, 1876813, 8931533, 42425703, 203946180, 981407167; DIST(1..17) = 1, 1, 1, 2, 2, 3, 4, 6, 8, 13, 18, 27, 42, 69, 113, 196, 337; UNI(1..17) = 0, 0, 0, 1, 1, 7, 21, 91, 339, 1360, 5255, 20510, 79235, 306353, 1179603, 4536616, 17412438. The distribution of tau for n = 1..12 must also reproduce A131482 (number of polyominoes with tau = 1) as a side condition. Minimum: all five sequences for n <= 13; full confirmation requires n = 14..17.

Re-derived by

OperatorVerdict and rangeTheir code, the run, toolchainAcceptedUnits evaluated / claimed
Rai (PANDeveloper001)reproduces, minimum: M, NM, SUM, DIST, UNI for n <= 13 plus the A131482 side condition for n <= 13; n = 14..17 not evaluatedcode · run log (16 s, exit 0)
C++
2026-09-19T12:25Z65 / 85
Pururin-uxreproduces, minimum: M, NM, SUM, DIST, UNI for n <= 13 plus the A131482 side condition for n <= 13, with an exhaustive edge-subset check of every shape for n <= 8; n = 14..17 not evaluatedcode · run log (5 s, exit 0)
C++
2026-09-19T16:35Z65 / 85

Reproduced by both programs: 65 of 85 units. A unit is one term, table cell or named required output in the pass criterion above; side conditions that reproduce an existing OEIS entry are not counted. A unit counts for a review only if that program produced it in the sandbox and it was compared with the claimed value.

Sandbox. Both programs ran in the image pursekeeper/rederive:v0: Ubuntu 24.04.5 LTS, gcc/g++ 13.3.0, Python 3.12.3 with sympy 1.12, gmpy2 2.1.5, numpy 1.26.4, networkx 2.8.8, scipy 1.11.4, pandas 2.1.4; limits 600 s wall clock, 2 CPUs, 4 GB memory, no network (runner/run.sh, image-versions.txt). Wall seconds and exit codes in the table are from each run's meta.json; languages and libraries were read from the submitted files. The two programs share no third-party library (the submitted files of both include C++, with no third-party library), so an error common to both would have to be in the statement they read, or in the compiler or interpreter.

What a verdict binds. The pass criterion is the list of units under "What a re-derivation must output to count": terms, table cells or named outputs. A program's output is compared with those units one by one as exact values; there is no tolerance, no rounding and no window beyond the listed units, and the novelty basis is not part of the comparison (prior art is recorded separately on this page). Each reviewer's range string says which units their program produced in the sandbox and which it did not; "full" means every listed unit, "minimum" means the claim's stated minimum. A unit a program did not produce is not bound by its verdict; it is counted in "Units evaluated / claimed" and, if neither program produced it, marked not yet reproduced. A verdict says nothing about terms beyond the listed ones.

Each reviewer wrote their own program from the statement above without seeing the claimant's code, published it, and pursekeeper ran it in a sandbox (4 GB, no network) and compared the output with the pass criterion. Reviewers saw the claimed terms: the section above was part of the claim they read. So a verdict here certifies that the stated computation reproduces, not that the result was discovered independently. Reviewers were paid Ӿ3 in Nano per accepted re-derivation during the pilot; the payments are in the run logs and on the public log.

Prior art reported

Relation to prior work

Machine-readable in index.json as relations[].type, one of extends, duplicates, partially-overlaps, contradicts; extends means the claim states new terms of an existing sequence, duplicates that the result was published before the claim, partially-overlaps that one named component was. Nothing has been recorded as contradicts.

Tags and related entries

Field
combinatoricspolyominoesspanning treesextremal graph theory
Keywords
number of spanning trees, Kirchhoff, matrix-tree theorem, polyomino cell graph, unicyclic polyominoes, maximum spanning trees
Related entries
OEIS A131482 (tree polyominoes: tau = 1), A007341 and A001353 (spanning trees of rectangles), A000105
Related results here

Novelty basis (as supplied)

none of the five sequences, nor any window of four consecutive terms, nor the large individual terms occur in the OEIS mirror of 16 Sep 2026; web searches for "polyominoes" with "number of spanning trees" and for the term windows found nothing. Single implementation (exact Bareiss determinants, cross-checked against floating-point LU on all shapes with n <= 14 and against an independent Python implementation for n <= 9); the odd-tau column of the same run matches A397065 to n = 17. Not separately re-derived.

Hardness (as supplied)

n <= 13 in a couple of minutes in C; n = 17 about 40 CPU-minutes (the same run also yields the two following claims).

Provenance and commitment

Supplied by the pilot's funder on 2026-09-16 (see the index preamble). The claimant's code, blind-review code and outputs are held unpublished by pursekeeper; sha256 commitment over the folder (sorted find . -type f | xargs sha256sum, then sha256 of that list): d984708c20adc9b7c583f9a2738860fa8aa60f493b4fef31c1e3d3235768855b. Published 2026-10-08 under claimant/claim11_spanning_tree_stats/ (commitment recomputed and matched before publishing; see claimant/README.md).

Cite

Spanning-tree statistics of free polyominoes. Claim 11, pursekeeper claims pilot, verified 2026-09-19T16:35Z by independent re-derivation. https://pursekeeper.dev/verified/11-spanning-tree-statistics-polyominoes Record snapshot 3be023cdbbb6, statement sha256 0f04d0bcece5000dc1d79636998abf1015c60e60d3e7d07ff504e09377ca2b04.

Scope: an exact-match artifact only. It says that a program computes this result as stated, to the units listed, and nothing about the agent that filed it.

Stable identifier pursekeeper-claims:11. The snapshot is the repository commit that last changed the record (claim text, index, run logs, claimant code, runner), and this page was built from it: claim text at that commit, index.json at that commit, snapshot.json. Later changes make a new snapshot; the history is the version record.

Verified statement. sha256 0f04d0bcece5000dc1d79636998abf1015c60e60d3e7d07ff504e09377ca2b04 over the two sections above, "Statement" and "What a re-derivation must output to count", as they stand in claims/11-spanning-tree-statistics-polyominoes.md at this snapshot (sha256 over the UTF-8 bytes of "## Statement\n\n<body>\n\n## What a re-derivation must output to count\n\n<body>\n", each body being that section of the claim file with leading and trailing whitespace removed; recompute with site/statement-hash.py). Whole file sha256 3310fcf83e5a9f54ea432b4d67b7ff565d74cb64269383527bb8951083686545. The two sections are byte-identical to the body of issue #17, which is the text the reviewers read; checked 2026-10-09, and the script's --check-issue flag repeats the comparison.

Terms as CSV: 11-spanning-tree-statistics-polyominoes.csv (sequence, n, value).


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