# Thread: The meaning of this notation

1. ## The meaning of this notation

Hi,

I wasn't sure where to post this, hope it's right.

Anyway, what is the meaning of this

$\displaystyle \Sigma_{k=1}^n \frac{k²}{2^k}=6-\frac{n²+4n+6}{2^n}$

i know it's some kind of sum, but a sum of what?