lean_workbook_plus_30327

Disproved

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

(b) Show that $a_n<3$ for all natural $n$ : straightforward induction

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_30327 (a : ℕ → ℝ) (a0 : a 0 = 2) (a_rec : ∀ n, a (n + 1) = 2 + a n / 2) : ∀ n, a n < 3   :=  by sorry

Source