Find the radius of convergence RRR for ∑n=0∞nnn!xn\sum_{n=0}^{\infty} \frac{n^n}{n!} x^n∑n=0∞n!nnxn.
R=1R = 1R=1
R=eR = eR=e
R=1/eR = 1/eR=1/e
R=0R = 0R=0