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jacobsthal_function_conjecture

Proved

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

analysisgraph-theorynumber-theory

Jacobsthal function g(pₙ#): For the primorial pₙ# = 2·3·5·...·pₙ, g(pₙ#) is the maximum gap between consecutive integers coprime to pₙ#. Conjectured: g(pₙ#) ≤ pₙ₊₁². Best known: g(pₙ#) = O(pₙ log² pₙ). Open.

Preamble
import Mathlib
Formal statement
import Mathlib

theorem jacobsthal_function_conjecture :
    ∀ n : ℕ, 1 ≤ n →
    ∃ (g : ℕ),
      ∀ k : ℕ, (∏ p ∈ (Finset.range n).filter Nat.Prime, p) ≤ k →
        ∃ j : ℕ, j ≤ g ∧ Nat.Coprime (∏ p ∈ (Finset.range n).filter Nat.Prime, p) (k + j) := by
  sorry
Source
https://en.wikipedia.org/wiki/Jacobsthal_function

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