1. Let http://stuff.daniel15.com/cgi-bin/mathtex.cgi?u%28n%29 denote the number of ways in which a set of http://stuff.daniel15.com/cgi-bin/ma...%5Cmbox%7Bn%7D elements can be partitioned into non-empty subsets. For example, http://stuff.daniel15.com/cgi-bin/ma...cgi?u%283%29=5, corresponding to:

http://stuff.daniel15.com/cgi-bin/ma...%7Ba,b,c%5C%7D

http://stuff.daniel15.com/cgi-bin/ma...0%5C%7Bc%5C%7D

http://stuff.daniel15.com/cgi-bin/ma...,%5C%7Bb%5C%7D

http://stuff.daniel15.com/cgi-bin/ma...5C%7Bb,c%5C%7D

http://stuff.daniel15.com/cgi-bin/ma...,%5C%7Bc%5C%7D

How do I do this?