1 2 3 4 n =- 1 12 July 8, 2019 16 32 64 128 1 2 3 4 5 6 n =- 1 12 proof 1 2 3 4 5 6 n =- 1 12 demonstration 1 2 3 4 5 n 1275 Proof 1 2 3 4 n =- 1 12 1 2 3 4 n 120 1 2 3 4 5 6 n =- 1 12 なぜ 1 2 + 3 4
