⊦ i * (j + j0) = i * j + i * j0
⊦ (i + 1) * (2 + i) * (2 * (i + 1) + 1) = 12 * i + (6 * i * i + 6 * 1) + i * (i + 1) * (2 * i + 1)
Used terms: 1, i * i, 6