Usually I see power series such as $$\sum_{n=0}^\infty \frac{n!}{(n)^n}z^n$$ Now, I am asked to find the radius of convergence for $$\sum_{n=0}^\infty 2^{-n}z^{n^2} \quad \text{ and } \quad \sum_{n=1}^\infty (3+4i)^n(z-4i)^n$$
How would I find the radius of convergence for those two power series?