AI-assisted certificate gives the proper hat-guessing number of K₈−e

The proper hat-guessing number of K₈−e is 14. A PGL(2,13)-equivariant fourteen-colour strategy uses 990 normalized twin decisions and a 48,510-edge residual-orbit matching; exhaustive checking covers all 138,378,240 proper colourings, and a general upper bound gives equality.

Sources for this record

What was already known

Adriaensen and coauthors gave a general upper bound but left this Kₙ−e endpoint case unresolved. Exact values for n=5, 6 and 7 are separate earlier results.

AI involvement AI-centered

The public submission credits GPT-5.6 Pro with construction search, certificate design, proof development and exact verification. Protti directed and repaired the work and set the claim scope.

The model contributed the retained equivariant construction, residual matching and certificate design under Protti’s direction.

Importance Modest

The exact strategy settles the eight-vertex case of the proper hat-guessing problem.

Limitations

The source reports exact certificate regeneration and exhaustive checking, but no named independent domain-expert review. A separate shared-completion companion remains review-pending.

Technical verification Formal (exact computation)

The source reports exact regeneration of the PGL action and matching, an independent orbit checker and a C++ sweep of all 138,378,240 proper colourings with zero uncovered cases. This certifies the finite strategy on a source-reported basis.

Formal checking

Exact group normalization, residual matching certificate and exhaustive game check

Checker
Data-only orbit/matching verifier and independent C++ full-colouring checker
Scope
Winning fourteen-colour strategy for K8−e over 138,378,240 proper colourings
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Few

The source credits Protti with direction and scope repair, but does not document his own explanation of the central matching construction. Few is the evidence default.

Correction and publication history