1 2 3 n formula proof July 8, 2019 16 32 64 128 1 2 3 4 5 to n formula proof 1 2 3 2 5 2 n 2 formula proof 1 x x 2 x 3 x n formula proof 1 4 2 4 3 4 n 4 formula proof 1= 2 proof
