AI-centered Lean proof classifies base-three partition counts

For partitions of {1,…,n} into nonempty blocks of at most three elements whose sums are powers of three, the count is exactly one on N_u={1,2,3,4}∪{3ᵗ+d:t≥2, d∈{−4,−2,−1,0,1,2,3,5}}; exactly two on E₂={13}∪{3ᵗ−3:t≥2}∪{3ᵗ−6:t≥3}; and at least three otherwise.

Sources for this record

What was already known

Gurvich and Naumova established existence for every n and identified some one- and two-partition cases. They conjectured more than two in the remaining cases.

AI involvement AI-centered

JD Jones directed the project. The classification and proof arose in consultation among Claude, GPT-6 and Grok, and Claude wrote the new Lean counting development; earlier existence work was retained with credit.

The classification and proof arose in human-directed consultation among AI systems, and Claude wrote the new counting development.

Importance Notable

The classification completes the base-three counting problem and gives infinitely many n=3ᵗ−6 with exactly two partitions, contradicting that conjecture.

Limitations

The result concerns only blocks of size at most three with sums powers of three. It does not address other bases or general m; the source authors have not endorsed the correction.

Technical verification Formal (Lean 4/Mathlib with decide +kernel exact finite search and induction)

The source reports kernel-checked exhaustive bases and a sorry-free Lean proof of the four universal classification theorems; independent Python counts supplement finite cases only. This review did not rerun the build.

Independent checking

Lean 4/Mathlib with decide +kernel exact finite search and induction

Checker
Lean 4 kernel
Scope
GNM.count_eq_one_iff, count_eq_two_iff, three_le_count_iff and count_eq_two_of_add_six
Basis
Reported by the linked checker
Evidence source

Human understanding Few

The detailed proof map is available, but no named human explanation of the central stabilization/frame mechanism is documented; Few is an evidence-gap default.

Correction and publication history

2026-10-18 · publication

The classification completes the base-three counting problem and gives infinitely many n=3ᵗ−6 with exactly two partitions, contradicting that conjecture.

Read this published revision