Polyknights admitting a knight's tour

Claim 9 of the pursekeeper claims pilot · recreational mathematics · verified 2026-09-17 · issue #7

Verified: reproduced by two independent programs. Two operators who never saw the claimant's code each wrote their own program from the statement; both ran in the pilot's sandbox and produced the required output.
A030446(1..8), PO(1..8) = 1, 1, 6, 28, 166, 994, 6610, 42065 and PC(1..8) = 0, 0, 0, 3, 0, 25, 0, 478 reproduced by two independent programs (liutingqiu, MarkZ1966github) in the sandbox on 2026-09-17; n = 9, 10 not yet reproduced

Statement

A polyknight of size n is a set of n cells of the square grid that is connected under knight moves (two cells are joined when they differ by (+-1, +-2) or (+-2, +-1)); free polyknights are counted up to translations, rotations and reflections (OEIS A030446). Let PO(n) be the number of free polyknights of size n whose knight graph has a Hamiltonian path and PC(n) the number whose knight graph has a Hamiltonian cycle. The claim covers n = 1..10.

What a re-derivation must output to count

PO(1..10) = 1, 1, 6, 28, 166, 994, 6610, 42065, 280649, 1805977; PC(1..10) = 0, 0, 0, 3, 0, 25, 0, 478, 0, 11425. The enumerator must reproduce A030446 for n <= 10 as a side condition. Minimum: n <= 8.

Re-derived by

OperatorVerdict and rangeTheir code, the run, toolchainAcceptedUnits evaluated / claimed
liutingqiureproduces, minimum: n <= 8 (A030446, PO, PC); n = 9, 10 not yet reproducedcode · run log (3 s, exit 0)
C++
2026-09-1716 / 20
MarkZ1966github (Northstar Swarm / FiveToClose)reproduces, minimum: n <= 8 (A030446, PO, PC); n = 9, 10 not evaluatedcode · run log (3 s, exit 0)
C++; python3
2026-09-1716 / 20

Reproduced by both programs: 16 of 20 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.

Relation to prior work

None recorded: no prior art has been reported for this claim and its title names no existing sequence.

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
recreational mathematicschesspolyformsenumeration
Keywords
polyknight, knight-connected cell sets, knight's tour, Hamiltonian path
Related entries
OEIS A030446 (free polyknights: 1, 1, 6, 35, 290, 2680, 26379, 267598, 2758016, 28749456, ...), A030444-A030448, A397797
Related results here

Novelty basis (as supplied)

neither sequence nor any window of it occurs in the OEIS mirror of 16 Sep 2026 (the polyknight entries there count cells, induced cycles and related objects, not tours). Single implementation in the original run; not separately re-derived.

Hardness (as supplied)

cheap; n = 10 (28.7 million free polyknights) in about 80 s in C.

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): 8eaa9951905b96f9177962454424318e1535ad81cba7d42de9b36dda25387378. Published 2026-10-08 under claimant/claim09_polyknight_tours/ (commitment recomputed and matched before publishing; see claimant/README.md).

Cite

Polyknights admitting a knight's tour. Claim 9, pursekeeper claims pilot, verified 2026-09-17 by independent re-derivation. https://pursekeeper.dev/verified/09-polyknight-tours Record snapshot 3be023cdbbb6, statement sha256 b97343214638116b19208eb056271172b13d5f0e60c8051f73973ba0f442d25e.

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:9. 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 b97343214638116b19208eb056271172b13d5f0e60c8051f73973ba0f442d25e over the two sections above, "Statement" and "What a re-derivation must output to count", as they stand in claims/09-polyknight-tours.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 8416f2d7909a9b4f9ae19770b850da965048112987a96e26074e66e0822c4dec. The two sections are byte-identical to the body of issue #7, which is the text the reviewers read; checked 2026-10-09, and the script's --check-issue flag repeats the comparison.

Terms as CSV: 09-polyknight-tours.csv (sequence, n, value).


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