Riemann Zeta Function (Part 4, beware)

The Riemann zeta function states that for every $s$ ,

$\zeta (s) = \displaystyle \sum_{n=1}^\infty \frac {1}{n^{s}}$ .

Sometimes these sums are divergent but using analytic continuation, you can get a finite answer.

Find $\zeta (1.5)$