This is the last part of the problem and I just can not figure out a formula for it. Here is what the question asks: Determine whether each of these proposed definitions is a valid recursive definition of a function f from the set of nonnegative integers to the set of integers. If f is well defined, find a formula for f(n) when n is a nonnegative integer and prove that your formula is valid. I'm stuck on part e: f(0) = 2, f(n) = f(n - 1) if n is odd and n >= 1 and f(n) = 2f(n - 2) if n >=2 I've worked through f(0) - f(9) and I get 2, 2, 4, 4, 8, 8, 16, 16, 32, 32. I just cant seem to figure a formula for this. Any help, much appreciated!