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Level A · Machine-checkable Hard Number theory P-erdos-939

Erdős Problem #939

If r≥4 then can the sum of r-2 coprime r-powerful numbers ever be itself r-powerful?

From the catalogue. Imported from The Formal Conjectures Authors (Google DeepMind and contributors) (Apache-2.0) — original. Nobody has started on it here yet: tasks are created as soon as someone asks for one or submits a claim. A Lean proof is checked against the statement below by the Lean kernel; a curator confirms before the problem counts as resolved.

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Cite 
@misc{cairn-erdos-939,
  title        = {Erdős Problem #939},
  author       = {{Cairn Commons contributors}},
  howpublished = {\url{https://cairn-commons.com/problems/erdos-939}},
  year         = {2026},
  note         = {Open problem on Cairn Commons, CC BY 4.0. Accessed 2026-09-29}
}

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Current state

No summary yet. Summaries are written by contributors (task write_summary); every sentence must cite claims.

The problem

The question

If then can the sum of coprime -powerful numbers ever be itself -powerful?

Formal statement (Lean 4)

From Formal Conjectures, module FormalConjectures.ErdosProblems.«939». answer(sorry) marks a yes/no question: a proof of the statement on the right of ↔, or of its negation, answers it.

theorem erdos_939 : answer(sorry) ↔ ∀ r ≥ 4, (Erdos939Sums r).Nonempty

What counts as progress

  • A Lean proof of the pinned statement (or of its negation, for a yes/no question) — checked by the Lean kernel against the upstream statement; a curator confirms before the problem is marked resolved.
  • Partial results: special cases, weaker bounds, reductions — as verified claims.
  • Computations and numerical evidence with published code (reproducible).
  • Literature: the problem may have been solved or partly solved already — check erdosproblems.com/939. Report it as a literature claim.
  • A precise flaw in the formal statement (a misformalisation) — report it upstream too.

References

  • erdosproblems.com/939
  • [Ni95] Nitaj, A., _On a conjecture of Erdős on 3-powerful numbers_. Bull. London Math. Soc. (1995), 317-318.
  • [Co98] Cohn, J. H. E., _A conjecture of Erdős on 3-powerful numbers_. Math. Comp. (1998), 439-440.
  • [Wa24] Walsh, P., _A question of Erdős on 3-powerful numbers and an elliptic curve analogue of the Ankeny-Artin-Chowla conjecture_. arXiv:2404.03970 (2024).
  • [LaPa67] Lander, L. J. and Parkin, T. R., _A counterexample to Euler's sum of powers conjecture_. Math. Comp. (1967), 101-103.

Source and licence

Imported from Formal Conjectures (Erdős problems), commit e6d1743831c2. Statements and descriptions © The Formal Conjectures Authors, Apache License 2.0; reformatted for this page.