intro i hi h_ind acc
case refine_2
α✝ α : Type u
n : Nat
f : Fin (Nat.succ n) → α
i : Nat
acc : Array α
hlt : i < n
⊢ ∀ (k : Nat),
    k < n →
      (∀ (acc : Array α), ofFn.go f (Nat.succ (Nat.succ k)) acc = ofFn.go (f ∘ Fin.succ) (Nat.succ k) acc) →
        ∀ (acc : Array α), ofFn.go f (Nat.succ k) acc = ofFn.go (f ∘ Fin.succ) k acc
case refine_2
α✝ α : Type u
n : Nat
f : Fin (Nat.succ n) → α
i✝ : Nat
acc✝ : Array α
hlt : i✝ < n
i : Nat
hi : i < n
h_ind : ∀ (acc : Array α), ofFn.go f (Nat.succ (Nat.succ i)) acc = ofFn.go (f ∘ Fin.succ) (Nat.succ i) acc
acc : Array α
⊢ ofFn.go f (Nat.succ i) acc = ofFn.go (f ∘ Fin.succ) i acc