AI-found graph refutes Written on the Wall II Conjecture 109

A connected 13-vertex graph formed by joining an independent seven-vertex set to two disjoint triangles has independence number 7, largest induced bipartite subgraph size 9 and Havel–Hakimi residue 2. These values violate Conjecture 109’s proposed bound of 6.

Sources for this record

What was already known

Conjecture 109 proposed the bound for every finite connected graph.

AI involvement AI-led

Andrii Vlasenko directed and released the work. His provenance record credits GPT-5.6 Sol Max with the search, witness, proof, formalization and verifier code.

The first-person repository assigns essentially every retained mathematical and checking artifact to the model, while recording human direction of the investigation.

Importance Modest

One finite witness refutes the universal graph inequality.

Limitations

The Lean check covers the 13-vertex witness. The repository also gives a symbolic counterexample family, which is outside that formal check.

Technical verification Formal (Lean 4 and exact exhaustive computation)

The repository reports a Lean 4 proof that the original universal inequality is false using an exact 13-vertex witness, plus exhaustive Python and independent C++ checks of its finite invariants. The general family is not required for the refutation; the reported checks were not rerun here.

Independent checking

Lean proof against the formal-conjectures definitions and a pinned Lean 4.27 build

Checker
Lean 4 kernel, reported by Vlasenko
Scope
The formal Conjecture 109 inequality is false for the connected 13-vertex witness with invariants 7, 9 and 2
Basis
Reported by the linked checker
Evidence source

Independent checking

Independent exact exhaustive subset and graph invariant calculations

Checker
The repository's Python and C++ verifiers
Scope
The same 13-vertex graph's independence, bipartite and residue values
Basis
Reported by the linked checker
Evidence source

Human understanding Few

The published explanation was model-written according to the provenance disclosure; no identified person's independent account of the residue and family mechanism was located. Few is the evidence default.

Correction and publication history