Even integral parts of powers of square roots

Ralf Stephan

For Z={α>1: some nonzero real ξ makes every floor ⌊ξαⁿ⌋ even for n≥1}, Stephan constructs a witness showing √3∈Z and proves that among integer square roots √m with m≥2, only √2 lies outside Z.

Sources for this record

What was already known

Dubickas asked whether √3 belongs to Z. The m=2 and m≥9 cases were known; several intermediate square roots were unresolved.

AI involvement AI-led

Stephan’s project disclosure credits Claude Fable 5 with the discovery and Fable 5 and Opus 5 with formalization. Stephan chose the problem, directed the work, revised the prose and checked statement alignment.

The attributed first-person account assigns the mathematical discovery to the agent, while Stephan directed and reviewed; the manuscript independently confirms substantial Claude Code collaboration.

Importance Notable

Answers Dubickas’s √3 question and completes the integer square-root classification.

Limitations

The Lean statements cover the √3 witness and classification. The paper’s separate divisibility and transcendental-witness results are outside this assessment.

Technical verification Formal (Lean 4 with leanprover/comparator)

The named √3 and classification statements have Lean 4 proofs. The repository describes comparator statement matching and standard-axiom checks, and Palomar reports a machine check at a cited commit. The paper’s unformalized §4.1 thickness calculation and §8 are outside the assessed theorems.

Independent checking

kernel type checking and comparator comparison of public challenge statements and permitted axioms

Checker
Lean 4 kernel and leanprover/comparator, as reported by Stephan and Palomar
Scope
SZ.sqrtThree_mem_MahlerZ and SZ.sqrt_natCast_mem_S_iff, matching Theorems A and B
Basis
Reported by the linked checker
Evidence source

Human understanding Full

Stephan’s exposition explains the two-scale reduction to base-m Cantor digits and the covering induction, and his attributed account says he directed and reviewed the result.

Correction and publication history