Number theory
Date added
$5,226 bounty1 piece from 1 personlast one 2 months ago
Nobody has attempted this. A complete proof or refutation takes the whole bounty.
A lemma, a definition, a special case. There is no race: when someone closes the problem, up to half of its bounty can go to the recognised pieces that led there.
contrib new erdos-849Command line, then a pull request on GitHub.
1 piece · 28 lemmas
2 Sept 2026
conjectures-tasks
The pinned statement, the Lean challenge file and the exact bundle you build against.
versions/fc-v2-erdos849-erdos-849-bcafe81896b7c30543e50b91-formalized →
conjectures-contribution
Every published piece for this problem, with its Lean source and its signed record.
contributions/erdos-849 →
Formal statement
Proof target
import Mathlib
import FormalConjectures.ErdosProblems.«849»
import TaskSupport
namespace Bounty
theorem target : fcTypeOfName% "Erdos849.erdos_849" := by
sorry
end Bounty
Original conjecture (Lean type)
True ↔ ∀ t ≥ 1, ∃ a, {n | ∃ k ≥ 1, 2 * k ≤ n ∧ n.choose k = a}.ncard = tOriginal conjecture source: FormalConjectures/ErdosProblems/849.lean
References
Something wrong with this formalization?
A statement that does not faithfully capture the original conjecture is the one real risk here, so we would rather hear about it early - before someone spends weeks on it.
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