Erdős problem 510
Chowla's cosine problem
Sources
FormalConjectures/ErdosProblems/
510.lean
Retained formal statement
Chowla's cosine problem
If is a finite set of positive integers of size then is there some absolute constant and such that
sorry ↔ ∃ c, ∃ (_ : 0 < c), ∀ᶠ (N : ℕ) in Filter.atTop, ∀ (A : Finset ℕ), 0 ∉ A → A.card = N → ∃ θ, ∑ n ∈ A, Real.cos (↑n * θ) < -c * √↑NOpenStatement only, no proof