I'm sorry that the thread title isn't descriptive at all, but I didn't know what to name it.

I have to take this sum:

sum from 0 to log base 2 of (n-1) of (n((3/2)^k)) - Wolfram|Alpha

and prove that for every positive integer n that is a power of 2, the sum is:

2(n^(log3/log2) - n)

can anyone help? thanks in advance