# librelist archives

## Series

### Series

From:
Aiden Hale
Date:
2014-05-04 @ 21:29
I’m noticing on the homework and examples online that a sub n or a sub n
plus 1 is used. What exactly IS a sub n though. Is it the function given?
or is it just another way of denoting the result of the function with a
given n?

### Re: [mat127weathers] Series

From:
Douglas Weathers
Date:
2014-05-04 @ 21:33
As an example take the series \sum 5^n / n!. Here, a_n = 5^n / n!, and
a_{n+1} = 5^{n+1} / (n+1)!.

Sometimes in power series we might write \sum a_n (x - c)^n as if the (x -
c) weren't part of the a_n, but you divide the whole thing in the ratio
test just the same: |x-c|^{n+1} / |x-c|^n = |x-c|.

On Sun, May 4, 2014 at 5:29 PM, Aiden Hale <hailaidenhale@gmail.com> wrote:

> I’m noticing on the homework and examples online that a sub n or a sub n
> plus 1 is used. What exactly IS a sub n though. Is it the function given?
> or is it just another way of denoting the result of the function with a
> given n?
>