Prime - Calculate sum of a sequence

[paul.hermans@benemtech.com]

If I have a sequence defined as:

an = 256(.25)^(n-1)

I can use the series app to evaluate various terms

How do i then determine the sum of the first 24 terms? I know how to do it by hand, but wondering if there is a quick function that I missed that does this for me.

Thanks

Paul