2009 Combinatorics #9 - Filling out a 3x3 Grid
Source:
January 7, 2012
Problem Statement
The squares of a grid are filled with positive integers such that is the label of the upper- leftmost square, is the label of the lower-rightmost square, and the label of each square divides the ne directly to the right of it and the one directly below it. How many such labelings are possible?