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Erdős problem 254

If A⊆NA \subseteq \mathbb{N} has unbounded dyadic-shell counts and ∑n∈A∥θn∥=∞\sum_{n \in A} \|\theta n\| = \infty for every 0<θ<10 < \theta < 1, must AA be complete - is every sufficiently large integer a sum of distinct elements of AA?

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The source's own material, retained exactly.

4 retained statements36c6d0fef71a

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FormalConjectures/ErdosProblems/

254.lean

Retained formal statement3 of 3

The hypothesis ¬ Summable (fun n : A ↦ distToNearestInt (θ * n)) used below says exactly that the partial sums of ‖θ n‖ over n ∈ A diverge, which is the form the linked proof uses. distToNearestInt is nonnegative, so this is an instance of not_summable_subtype_iff_tendsto_sum_indicator.

FormalConjectures/ErdosProblems/254.leanErdos254.not_summable_iff_tendsto_partial_sums4 linesExact file
∀ (A : Set ℕ) (θ : ℝ),  (¬Summable fun n => distToNearestInt (θ * ↑↑n)) ↔    Filter.Tendsto (fun N => ∑ n ∈ Finset.range N, A.indicator (fun n => distToNearestInt (θ * ↑n)) n) Filter.atTop      Filter.atTop
APIStatement only, no proof