| m0 ≤ m, m ≤ n ⊦ (m * (m + 1)) / 2 + m0 < ((n + 1) * (n + 2)) / 2, n < m, ((n + 1) * (n + 2)) / 2 < ((m + 1) * (m + 2)) / 2 |
⊦ m < n ↔ ¬ n ≤ m
((m + 1) * (m + 2)) / 2 ≤ ((n + 1) * (n + 2)) / 2, m ≤ n, m0 ≤ m ⊦ n < m, (m * (m + 1)) / 2 + m0 < ((n + 1) * (n + 2)) / 2
Used terms: ((m + 1) * (m + 2)) / 2, ((n + 1) * (n + 2)) / 2