Discussion area to prepare for Exam 2
To find the radius of convergence of $ \sum_{n=0}^\infty (n!)z^{n!} $, you'll need to use the Ratio Test.
$ \frac{u_{n+1}}{u_n}=\frac{(n+1)!z^{(n+1)!}{n!z^{n!}=(n+1)z^{n\cdot n! $.
Ask yourself what that does as n goes to infinity in case |z|<1, =1, >1.
