The number which best completes the sequence below is1 5 17 53 161?

Answer 1

Here is one way to describe this sequence:

a(0)=1

a(n) = 3*a(n-1) + 2 a(n) = 2*3^n - 1

So we have:

1, 5, 17, 53, 161, 485, 1457, 4373, 13121, 39365, 118097, 354293, 1062881, 3188645, 9565937, 28697813, 86093441, ...