exact ⟨n+1, rfl⟩
case cons.mp.intro.intro
α✝ : Type
n : Nat
ih : (∀ (x : Clause α✝), x ∈ List.replicate n [] → x = []) ↔ ∃ n_1, List.replicate n [] = List.replicate n_1 []
⊢ ∃ n_1, [] :: List.replicate n [] = List.replicate n_1 []
no goals