conv =>
  change bitwise and n (2^k*2 - 1) = n % (2^k*2)
  rw [Nat.mul_comm _ 2]
k : Nat
h_ind : ∀ (n : Nat), n &&& 2 ^ k - 1 = n % 2 ^ k
n : Nat
⊢ n &&& 2 ^ succ k - 1 = n % 2 ^ succ k
k : Nat
h_ind : ∀ (n : Nat), n &&& 2 ^ k - 1 = n % 2 ^ k
n : Nat
⊢ bitwise and n (2 * 2 ^ k - 1) = n % (2 * 2 ^ k)