# Homework Help: Summation simplification help

1. Jul 14, 2008

### withoutwax

I am wondering whether the following expression can be simplified

sum of( (p^n) / (n!) ) from n=1 to n=n.

2. Jul 14, 2008

### Dick

Re: Summation

It look pretty simple to me already. If you mean write it without the summation, I don't think so.

3. Jul 14, 2008

### HallsofIvy

Re: Summation

What do you mean by "n= n"? Did you mean
$$\sum_{n=1}^{N} \frac{p^n}{n!}$$?
I don't see any simple way to write that. However, it is well known that
$$\sum_{n=1}^\infty \frac{p^n}{n!}= e^p- 1$$