| (i1 + 1) * fac(i1) ≤ (i2 + 1) * fac(i2), fac(i1) ≤ fac(i2) ↔ i1 ≤ i2, 0 ≤ i1, 0 ≤ i2, ∀ i0, j. i→n(i0) < i→n(i1 + 1) → 0 < i0 ∧ 0 < j → (fac(i0) ≤ fac(j) ↔ i0 ≤ j) ⊦ i1 ≤ i2 |
(i1 + 1) * fac(i1) ≤ (i2 + 1) * fac(i2), 0 ≤ i1, 0 ≤ i2, i2 < i1, fac(i2) < fac(i1), 0 < i1, ∀ i0, j. i→n(i0) < i→n(i1 + 1) → 0 < i0 ∧ 0 < j → (fac(i0) ≤ fac(j) ↔ i0 ≤ j) ⊦
Used simplifier rules: forward-le-05: ⊦ i < j ∧ 0 ≤ i → 0 < j; (forward) from specification int-abs%lels-01: ⊦ ¬ i ≤ j ↔ j < i; from specification int-abs