Fix a positive integer n. How many sequences (a

_{1}, a_{2}, ... , a_{n}) of positive integers are there with the property that at most i of the terms are greater than n-i, for all i = 0,1,...,n?

Source:Richard Stanley (MIT) posed this problem as a warm-up for a recent talk he gave at Harvey Mudd.© Copyright 1997 Stan Wagon. Reproduced with permission.

2 October 1998