# Need help evaluating this sum

1. Sep 4, 2006

### JasonJo

i need help evaluating this sum:

(that is 100 P i, or the permutation)

Last edited: Sep 17, 2008
2. Sep 4, 2006

### HallsofIvy

What does "100 P i" mean with i going from 1 to 100? Is P a constant?

3. Sep 4, 2006

### shmoe

I can't see your attatchment. Does 100 P i mean the number of permuations of i objects selected from 100? namely, 100 P i= 100!/(100-i)!

What's being summed?

4. Sep 4, 2006

### JasonJo

yeah i'm sorry if it came out bad, but yeah it's the permutation

5. Sep 4, 2006

### shmoe

So what's being summed then?

6. Sep 4, 2006

### CRGreathouse

I'm going to take a stab in the dark and guess you mean

$$\sum_{i=0}^n{}_{100}P_i$$

Am I close?

7. Sep 4, 2006

### JasonJo

yeap, that's exactly it. is there any explicit way to calculate the sum for arbitrary n?