Prime - Calculate sum of a sequence

[Joe Horn]

(08-26-2014 06:31 AM)Bill Zimmerly Wrote:  

(08-26-2014 05:01 AM)paul.hermans@benemtech.com Wrote:  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

1. Apps "Function."

2. Set F1(X)=256*(.25)^(X-1).

3. Home.

4. "Template" button (the third one to the right from "Vars."

5. Choose the Sigma summation (down two, right two).

6. Set X=1 to 24 and F1(X).

I got 341.3333333334 as the answer.

If you really do want to use the Sequence app instead of the Function app, follow Bill's instructions but use U1 instead of F, and N instead of X. But this particular example doesn't define the sequence based on previous terms (which is what the Sequence app does), so the Function app is more apt for it.