Given f(x)=∑n=0∞anxnf(x) = \sum_{n=0}^{\infty} a_n x^nf(x)=∑n=0∞anxn with an=1n!a_n = \frac{1}{n!}an=n!1, find the radius of convergence RRR.
R=∞R = \inftyR=∞
R=1R = 1R=1
R=0R = 0R=0
R=eR = eR=e