Finding the radius of convergence.... 1. The problem statement, all variables and given/known data 1+2x+(4x^(2)/2!)+(8x^(3)/3!)+(16x^(4)/4!)+(32x^(5)/5!)+... 2. Relevant equations I would use the ratio test. Which is.... lim as n→∞ (An+1/An) 3. The attempt at a solution I know what to do to find the answer, but I don't know how to find the expression for the provided series. I'm guessing it's ((2x^(n))/n!), then work with the ratio test from there?