mを4で割った余りで場合分けする。 m = 4kのとき n = 12k, a = 6k, S1 = 9k2 b = 2k-1, S2 = 3k2, S3 = 6k-1 m = 4k+1のとき n = 12k+3, a = 6k+1, S1 = 9k2+3k b = 2k, S2 = 3k2+3k+1, S3 = 6k+1 m = 4k+2のとき n = 12k+6, a = 6k+3, S1 = 9k2+9k+2 b = 2k…