Symmetric pattern-avoiding permutations are restricted permutations which are invariant under actions of certain subgroups of D_4, the symmetry group of a square. I'll be talking about pattern-avoiding permutations with 180 degree rotational-symmetry. In particular, I'll use combinatorial techniques to enumerate symmetric permutations which avoid one pattern of length three and one pattern of length four.
Graduate Student Combinatorics Seminar
Wednesday, February 24, 2010 - 12:45pm
David Lonoff
University of Pennsylvania