(i0 + 1) % 2 = 0, prime(i0 + 1) ⊦ i0 % 2 = 0, 1 = i0
prime(i0 + 1) ⊦ (i0 + 1) % 2 = 0, i0 % 2 = 0, 1 = i0
Used formulas: (i0 + 1) % 2 = 0