| 0 ≤ i, 0 ≤ j, fac(i + 1 - j) * fac(j - 1) | fac(i), fac(i - j) * j * fac(j - 1) | fac(i), 0 < j, 0 < i, j ≤ i, fac(i - j) | fac(i) * fac(i + 1 - j) ⊦ fac(i + 1 - j) = (i + 1 - 2 * j) * fac(i - j) + fac(i - j) * j |
⊦ (i + i0) * j = i * j + i0 * j
0 ≤ i, 0 ≤ j, fac(i + 1 - j) * fac(j - 1) | fac(i), fac(i - j) * j * fac(j - 1) | fac(i), 0 < j, 0 < i, j ≤ i, fac(i - j) | fac(i) * fac(i + 1 - j) ⊦ fac(i + 1 - j) = ((i + 1 - 2 * j) + j) * fac(i - j)
Used simplifier rules: commutativity: ⊦ i * j = j * i; from specification int-mult Used terms: j, fac(i - j), i + 1 - 2 * j