Hello PF. 1. The problem statement, all variables and given/known data A function f is defined by f(x) = 1 + 2x + x2 + 2x3 + x4 + 2x5 + x6... Find the radius of convergence of the series and the explicit formula for f(x). 2. Relevant equations 3. The attempt at a solution I know that the formula for the series is going to be similar to the function xn2c, where c is some expression dependent on n that is equal to 1 when n is odd and equal to 0 when n is 0 or when n is even. However, I'm having difficulty finding what c actually is in terms of n. Maybe there's something obvious that I'm not seeing here?