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Erdős problem 349

For 0<α≤10 < \alpha \le 1 and any t>0t > 0, (t,α)(t, \alpha) is not a good pair: every term ⌊tαn⌋\lfloor t\alpha^n\rfloor lies in the finite interval [0,⌊t⌋][0, \lfloor t\rfloor] (since αn≤1\alpha^n \le 1), so every subset sum is bounded by the constant ∑i∈[0,⌊t⌋]i\sum_{i \in [0,\lfloor t\rfloor]} i, and no large integer can be a subset sum. A partial result on the open Erdős Problem 349, complementing the 2<α2 < \alpha and integer-coefficient cases.

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FormalConjectures/ErdosProblems/

349.lean

Retained formal statement8 of 12

Binary expansion. Every natural number kk is a sum of distinct powers of two: there is a finite set EE of exponents with k=∑i∈E2ik = \sum_{i \in E} 2^i. Proved by strong induction: subtract the largest power 2m≤k2^m \le k, recurse on the remainder.

FormalConjectures/ErdosProblems/349.leanErdos349.exists_finset_sum_two_pow1 lineExact file
∀ (k : ℕ), ∃ E, k = ∑ i ∈ E, 2 ^ i
SolvedProof has a holeformal conjecturesexternal proof

The proof uses `sorry`: part of the argument is written but not proved. Lean accepts the file; it does not accept the theorem.