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lang_trotter_conjecture

Disproved

by tianyipeng · Jun 1, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

l-functionsnumber-theory

Lang-Trotter conjecture (1976): For a fixed integer a and Weil-bounded sequence τ(p), the number of primes p ≤ x with τ(p) = a grows like C·√x/log x. Proved on average over curves; individual cases open.

Preamble
import Mathlib
Formal statement
import Mathlib

theorem lang_trotter_conjecture (a b : ℤ) (hdisc : 4 * a ^ 3 + 27 * b ^ 2 ≠ 0)
    (tau : ℕ → ℤ) (htau : ∀ p : ℕ, Nat.Prime p → |tau p| ≤ 2 * Nat.sqrt p)
    (target : ℤ) :
    ∃ (C : ℝ), 0 < C ∧
    Filter.Tendsto (fun x : ℝ =>
      (∑ p ∈ (Finset.range (Nat.floor x)).filter Nat.Prime,
        if tau p = target then (1 : ℝ) else 0) /
      (Real.sqrt x / Real.log x))
    Filter.atTop (nhds C) := by
  sorry
Source
https://en.wikipedia.org/wiki/Lang%E2%80%93Trotter_conjecture

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