# Erdős Problem 421

A statement in qed.bot, the register of claims of AI work in mathematics. The register grades the evidence attached to each claim; it never rules on whether a proof is correct.

- Identifier: erdos:421
- Collection: Erdős
- Page: https://qed.bot/s/erdos-421
- Formal record: solved; at its source: solved
- Machine-checked: no independent check has verified it
- Fidelity F2: The statement corpus cites this proof against its own statement.
- Source: https://www.erdosproblems.com/421

## AI claims

No AI contribution is recorded against this statement.

## Claimed on erdosproblems.com

Proof claims posted on erdosproblems.com, which says that listing a claim is no guarantee of proof correctness. Nobody has examined them, and none counts in the register's totals.

- Animish Sharm, using Claude: a full proof claimed, 26 Jul 2026. Autonomy A?, evidence V0. https://www.erdosproblems.com/forum/thread/421/proof-claims#proof-claim-144
- Rob Sneiderman, using GPT 5.6 Sol Ultra: a full proof claimed, 21 Jul 2026. Autonomy A?, evidence V0. https://www.erdosproblems.com/forum/thread/421/proof-claims#proof-claim-100

## Formal statements

- FormalConjectures/ErdosProblems/421.lean, https://github.com/google-deepmind/formal-conjectures/blob/main/FormalConjectures/ErdosProblems/421.lean

Cite as: qed.bot, "Erdős Problem 421", https://qed.bot/s/erdos-421, as of 30 Sep 2026. The register's data is published under CC BY 4.0: https://creativecommons.org/licenses/by/4.0/