lean_workbook_plus_34888

Proved

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

Find the closed form of the sequence $(a_n)$ defined as $a_0=1,a_1=2$ and $a_{n+2}=4a_{n+1}+a_n$ .

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_34888 (a : ℕ → ℝ) (a0 : a 0 = 1) (a1 : a 1 = 2) (a_rec : ∀ n, a (n + 2) = 4 * a (n + 1) + a n) : ∃ f : ℕ → ℝ, ∀ n, a n = f n   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook

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