# Writing an expression in summation notation

1. Jan 29, 2012

### SithsNGiggles

How would I write

1 + n + n(n - 1) + n(n - 1)(n - 2) + ･･･ + n!

in sigma notation? If it's possible.

2. Jan 29, 2012

### JHamm

$$\sum_{i = 0}^{n} \frac{n!}{(n - i)!}$$