| j ≤ i, 0 < i, 0 < j, fac(i - j) * fac(j) | fac(i), fac(i + 1 - j) * fac(j - 1) | fac(i), 0 ≤ j, 0 ≤ i ⊦ (fac(i) * fac(i + 1 - j)) / fac(i - j) = fac(i) * (i + 1 - 2 * j) + (fac(i) * fac(j)) / fac(j - 1) |
⊦ j | i ∧ j ≠ 0 → (i / j = i0 ↔ i = i0 * j)
¬(fac(i - j) | fac(i) * fac(i + 1 - j) ∧ fac(i - j) ≠ 0), j ≤ i, 0 < i, 0 < j, fac(i - j) * fac(j) | fac(i), fac(i + 1 - j) * fac(j - 1) | fac(i), 0 ≤ j, 0 ≤ i ⊦ (fac(i) * fac(i + 1 - j)) / fac(i - j) = fac(i) * (i + 1 - 2 * j) + (fac(i) * fac(j)) / fac(j - 1)
fac(i - j) | fac(i) * fac(i + 1 - j) ∧ fac(i - j) ≠ 0, j ≤ i, 0 < i, 0 < j, fac(i - j) * fac(j) | fac(i), fac(i + 1 - j) * fac(j - 1) | fac(i), 0 ≤ j, 0 ≤ i ⊦ fac(i) * fac(i + 1 - j) = (fac(i) * (i + 1 - 2 * j) + (fac(i) * fac(j)) / fac(j - 1)) * fac(i - j)
Used terms: fac(i) * (i + 1 - 2 * j) + (fac(i) * fac(j)) / fac(j - 1), fac(i - j), fac(i) * fac(i + 1 - j)