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Erdős problem 41 Let A ⊂ N A \subset \mathbb{N} A ⊂ N be an infinite set such that the triple sums a + b + c a+b+c a + b + c are all distinct
for a , b , c ∈ A a,b,c \in A a , b , c ∈ A (aside from the trivial coincidences). Is it true that
lim inf N → ∞ ∣ A ∩ { 1 , … , N } ∣ N 1 / 3 = 0 ? \liminf_{N \to \infty} \frac{\lvert A \cap \{1,\ldots,N\}\rvert}{N^{1/3}}=0? N → ∞ lim inf N 1/3 ∣ A ∩ { 1 , … , N }∣ = 0 ?
$3,980 bounty · nobody has started
week of 30 Sept 2025 · nothing published week of 7 Oct 2025 · nothing published week of 14 Oct 2025 · nothing published week of 21 Oct 2025 · nothing published week of 28 Oct 2025 · nothing published week of 4 Nov 2025 · nothing published
Solve it Nobody has attempted this. A complete proof or refutation takes the whole bounty.
Add the first piece Even one lemma helps. Whoever finishes this later shares the pool with everyone who got them there.
Command line, then a pull request on GitHub.
← Erdős problem 39 Erdős problem 44 →
What has been built Nothing has been published against this problem yet.
A first lemma is worth as much as a last one: whoever closes the problem shares the pool with everyone who got them there.
Disproof target
import FormalConjectures.ErdosProblems.«41»
import TaskSupport
namespace Bounty
theorem target : ¬ (fcTypeOfName% "Erdos41.erdos_41") := by
sorry
end Bounty
Open this target’s Challenge.lean Original conjecture (Lean type)
∀ (A : Set ℕ),
Erdos41.NtupleCondition A 3 →
A.Infinite → Filter.liminf (fun N => ↑(A ∩ Set.Icc 1 N).ncard / ↑N ^ (1 / 3)) Filter.atTop = 0Original conjecture source: FormalConjectures/ErdosProblems/41.lean
Source type SHA-256 sha256:3971d1ee8c9f8b43524f50508403069af8a12d5ad4e2ea3668e0f4e097497ab4
Task id fc-6a786f99-erdos41-erdos-41-824fabe4fc-counterexample-v1
Task commitment sha256:6e8709da532a2c87489c88070177b82c5ce6837d608584faa33e3bdfbdb8bfee week of 11 Nov 2025 · nothing published
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30 Sept 2025 nothing published against this one yet 22 Sept 2026
erdosproblems.com/41
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.
Our channel is in the Bittensor Discord server. Join the server first, then open the channel to send your report.
Reward
$3,980
for closing this problem
Whoever closes it takes the bounty. Published pieces that helped get there share a separate contribution pool, paid out once the problem is closed.
Set by bounty policy linear-age-v3-locked: the amount is worked out from how long the problem has stood open, so it moves as the pool and the pool's age profile move.
Prove it or break it
The same problem accepts both. You can submit a proof of the statement or a counterexample that refutes it, and you choose which when you submit.
Prove the statement no attempts
Find a counterexample no attempts
Erdős problem 41 · Conjectures.io