N 3 2n 2 9n 18 July 8, 2019 16 32 64 128 N 3 2n 2 9n 18 0 (18 ^ n)/(3 ^ (2n - 1) * 2 ^ (n - 2)) (18 ^ (n + 3))/(3 ^ (2n + 5) * 2 ^ (n - 2)) N 3 n
