A power series that converges for $|z| \leq 1$ and diverges otherwise.

I need to find a power series $\sum a_n z^n$ that converges for $|z| \leq 1$ and diverges otherwise.

I think I have one I just want to be sure.

So, the series:

$$\sum \frac{z^n}{n^2}$$

has radius of convergence of $1$. So it converges when $|z| <1$ and diverges when $|z| >1$, correct?

And we know it converges at $z= \pm 1$ by the comparison test, correct? This part is where I'm having trouble with. Could someone explain in detail how to use the comparison test with this? I know the comparison test says, "if you have two series $\sum a_n$ and $\sum b_n$ with $a_n, b_n \geq0$ and $a_n \leq b_n$, then if $\sum b_n$ converges, then $\sum a_n$ converges." But what other series would you use in the comparison test. I also know that $|\frac{z^n}{n^2}|= \frac{1}{n^2}$. Can you use this fact?

Please help! This series would work correct?