http://i37.tinypic.com/2nhosqa.jpg

i tried:

$\displaystyle

x_i=\frac{1}{i^s}

$

i from 1 to infinty

the whole sum is called u

$\displaystyle

\left \| u \right \|_p=(\sum_{n=1}^{\infty}(\frac{1}{i^s})^p)^\frac{ 1}{p}$

and i think we need to show that i converges

but thats only a shot in the dark

i dont have a clue about it