lean_workbook_plus_59775

Proved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

Show that there are no functions $f:\mathbb{N}\to \mathbb{N}$ such that $2f(n)> f(n-1)+f(n+1)\quad \forall n>1.$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_59775 (f : ℕ → ℕ) (hf: ∀ n:ℕ, n > 1 → 2 * f n > f (n-1) + f (n+1)) : False   :=  by sorry

Source