n * n + n = m0 * 2 + n0, n0 < 2, m0 ≤ n ⊦ n = 1, n = 0, m0 = 1, m0 = 0
Used simplifier rules: twols-02: ⊦ m ≠ 0 → (m < 2 ↔ m = 1); from specification nat-basic1