Suppose there are n people in an office. At Christmas they have a random gift exchange in which every name is writen on scraps of paper, mixed around in a hat, and then everyone draws a name at random to determine who they are to get a gift for.

What is the probability nobody draws their own name?

I read that each number for n gift people followed a pattern:



n: H(n)

-----

1: 0

2: 1

3: 2

4: 9

5: 44

6: 265

7: 1854

8: 14853



Multiply the H(n-1) by the n people, then add 1 if n is odd and subtract 1 if n is even to get H(n)

Posted by Gamer on 2003-10-11 08:59:20