## Exploring the number of different ways a number can be expressed as a sum of powers of 2.

### Problem 169

Published on Friday, 23rd November 2007, 09:00 pm; Solved by 2355

Define f(0)=1 and f(n) to be the number of different ways n can be expressed as a sum of integer powers of 2 using each power no more than twice.

For example, f(10)=5 since there are five different ways to express 10:

1 + 1 + 8
1 + 1 + 4 + 4
1 + 1 + 2 + 2 + 4
2 + 4 + 4
2 + 8

What is f(1025)?