Prime - Calculate sum of a sequence
08-26-2014, 05:01 AM
Post: #1
 paul.hermans@benemtech.com Junior Member Posts: 9 Joined: Aug 2014
Prime - Calculate sum of a sequence
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
08-26-2014, 06:31 AM
Post: #2 Bill Zimmerly Junior Member Posts: 37 Joined: Jun 2014
RE: Prime - Calculate sum of a sequence
(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.
08-26-2014, 12:01 PM
Post: #3 Joe Horn Senior Member Posts: 1,624 Joined: Dec 2013
RE: Prime - Calculate sum of a sequence
(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.

<0|ɸ|0>
-Joe-
08-26-2014, 10:47 PM
Post: #4
 paul.hermans@benemtech.com Junior Member Posts: 9 Joined: Aug 2014
RE: Prime - Calculate sum of a sequence
Thanks guys, that is exactly what I needed.....never thought to do it that way at all.

Still learning my way around this calculator.

Paul
08-27-2014, 06:12 AM
Post: #5 Bill Zimmerly Junior Member Posts: 37 Joined: Jun 2014
RE: Prime - Calculate sum of a sequence
You're welcome, Paul. - Bill
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