1 3 5 7 9 2n 1 July 8, 2019 16 32 64 128 1 3 5 7 9 2n 1 formula 1 3 5 7 9 2n 1 sum formula 1 3 5 7 9 2n 1 n 2 1 3 5 7 9 2n 1 公式 1 3 9 27 pattern rule 1 + 3 + 5 + 7 + 9
