Adam Goyt’s solution to Problem 11567 from “The American Mathematical Monthly” was selected for publication and appeared in the April 2013 issue.

The problem was to enumerate the number of permutations of the multiset {1,1,2,2,…,n,n} with certain restrictions. He and Lara Pudwell of Valparaiso University produced a bijection that showed that this set of restricted permutations of this multiset has sum(2^{n-k}*S(n,k),k=0..n) elements, where S(n,k) is the Stirling number of the second kind.