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Quasipolynomial Bounds for Arithmetic Progressions

OpenAI · September 23, 2026

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Abstract

We prove Erdős's conjecture that every set of positive integers with divergent reciprocal sum contains arithmetic progressions of every finite length. More quantitatively, for every fixed k ≥ 3, we show $\displaystyle r_k(N)\le C_kN\exp\bigl(-c_k(\log N)^{\varepsilon_k}\bigr)$ with $C_k,c_k,\varepsilon_k\gt 0$, where $r_k(N)$ is the largest size of a subset of $\{1,\ldots,N\}$ with no nonconstant k-term arithmetic progression.

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Collected automatically by AI tools (Claude Opus 5.5 and GPT-6 Astra, 2026-10-21) and not checked by a person. May be wrong or incomplete. Report an error.

Comments and discussion

  • Thomas Bloom, Erdős problems in the OpenAI proofs, with comment thread (MalekZ, jleng01, Thomas Bloom) (erdosproblems.com blog and forum, 8–12 Oct 2026). Bloom summarizes the claimed bound for all k ≥ 3, notes that a bound of this shape was already known for k=3 (Kelley–Meka), and says the Lean code "appears to prove the weaker bound" exp(-(log log N)^{1+c_k})N. In the comments, jleng01 calls the proof "largely a synthesis of previous work on the problem," and Bloom agrees that it shows existing techniques "pushed sufficiently far" suffice.

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Cite

@misc{OAI:Quasipolynomial-Bounds-for-Arithmetic-Progressions-September-23-2026,
  author = {{OpenAI}},
  title = {{Quasipolynomial Bounds for Arithmetic Progressions}},
  howpublished = {OpenAI Math Release preprint
                  \href{https://github.com/openai/math/blob/main/preprints/Quasipolynomial-Bounds-for-Arithmetic-Progressions-September-23-2026/paper.pdf}{OAI:Quasipolynomial-Bounds-for-Arithmetic-Progressions-September-23-2026}},
  year = {2026}
}

Lean formalization

OpenAI provides Lean files for this family: lean/docs/159.md. The Lean statements have not been checked by people against the paper's claims.

Family 159: Erdős’s reciprocal-sum conjecture and quasipolynomial Szemerédi bounds

Proves Erdős's conjecture that every set of positive integers with divergent reciprocal sum contains arithmetic progressions of every finite length. Quantitatively, for each fixed k ≥ 3, every subset of $\{1,\ldots,N\}$ with no nonconstant k-term progression has size at most $C_kN\exp[-c_k(\log N)^{\varepsilon_k}]$, with positive constants depending only on k.

This is the only paper in this family.