| j * (j + 1) < (i0 + 1) * 2, j * (j + 1) = i0 * 2 + j0, j0 < 2, i0 ≤ j, 0 ≤ j, 2 ≤ j, 0 < j, 0 ≤ j0, j0 < j, 0 ≤ i0 ⊦ j * (j + 1) < (i0 + 1) * j, j = 0 |
⊦ i < j ∧ j ≤ j0 → i < j0
¬(j * (j + 1) < (i0 + 1) * 2 ∧ (i0 + 1) * 2 ≤ (i0 + 1) * j), j * (j + 1) < (i0 + 1) * 2, j * (j + 1) = i0 * 2 + j0, j0 < 2, i0 ≤ j, 0 ≤ j, 2 ≤ j, 0 < j, 0 ≤ j0, j0 < j, 0 ≤ i0 ⊦ j * (j + 1) < (i0 + 1) * j, j = 0
Used terms: (i0 + 1) * 2, (i0 + 1) * j, j * (j + 1)