1.
Suppose f:R(0,)f : \mathbb{R} \to (0, \infty) is a differentiable function such that 5f(x+y)=f(x)f(y)5f(x + y) = f(x)f(y), x,yRx, y \in \mathbb{R}. If f(3)=320f(3) = 320, then n=05f(n)\sum_{n=0}^{5} f(n) is equal to