AI-assisted Lean proof resolves the factorial divisor-sum irrationality problem for all exponents

For every natural k≥0, the convergent series Σₙ≥1 σₖ(n)/n! is irrational, where σₖ(n) is the sum of kth powers of positive divisors of n. The k>0 cases answer Erdős Problem 252; the Lean theorem also handles k=0.

Sources for this record

What was already known

The problem catalog asked for all positive exponents. Pratt proved the k=4 case and described earlier partial results; the project’s all-exponent proof is presented as an original development rather than a formalization of a published general proof.

AI involvement AI-centered

Tokengrinder directed the target, proof obligations, reviews and publication. The Palomar account says Codex and Claude agents supplied substantive mathematical proof construction and Lean work; finer per-agent attribution was not consistently recorded.

Tokengrinder directed the target, obligations and review. The project account credits Codex and Claude agents with substantive all-exponent proof construction as well as Lean development, without reliable finer per-agent attribution.

Importance Notable

Gives one proof of the full exponent family in a named Erdős problem, beyond the previously cited special cases.

Limitations

The source warns its literature search is not exhaustive and does not claim transcendence or relations among different sums. It reports a completed local Lean proof and statement audit, but no independent human expert review; Palomar registration status is separate.

Technical verification Formal (Lean)

The source reports full build, trust-zero rebuild, statement and axiom audits, and fresh kernel replay of the all-exponent theorem. This applies to the selected claim and is not an independent reproduction by AIProofWatch.

Formal checking

The source reports a source-only Lean proof with no holes, a trust-level-zero statement audit, standard-axiom check and fresh leanchecker replay. The Challenge placeholder is not imported into Solution.

Checker
Lean 4 kernel and documented local statement, axiom or certificate audits run by repository authors
Scope
For every natural k≥0, the convergent series Σₙ≥1 σₖ(n)/n! is irrational, where σₖ(n) is the sum of kth powers of positive divisors of n. The k>0 cases answer Erdős Problem 252; the Lean theorem also handles k=0.
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 project reports agent review and the human author’s direction but no independent human expert review or human explanation of the full proof mechanism. Few is the evidence default.

Correction and publication history

2026-10-18 · publication

Claim-level primary-source review of exact theorem, prior baseline, AI contribution and documented checking scope.

Read this published revision