COMBINATORICS
2002
13 years 4 months ago
2002
Let In() denote the number of involutions in the symmetric group Sn which avoid the permutation . We say that two permutations , Sj may be exchanged if for every n, k, and order...
DM
2008
13 years 4 months ago
2008
We give some new Wilf equivalences for signed patterns which allow the complete classification of signed patterns of lengths three and four. The problem is considered for pattern a...