$\sum_{n=1}^{\infty} \frac{1}{n}$ (p-series with $p=1$)

$\sum_{n=1}^{\infty} \frac{1}{n^2}$ (p-series with $p=2$)

$\sum_{n=1}^{\infty} \frac{n}{n^4} = \sum_{n=1}^{\infty} \frac{1}{n^3}$ (p-series with $p=3$)

$\sum_{n=1}^{\infty} \frac{1}{n^4}$ (p-series with $p=4$)