Restricted permutations by patterns of type
arXiv:math/0202219
Abstract
Recently, Babson and Steingrimsson (see \cite{BS}) introduced generalized permutations patterns that allow the requirement that two adjacent letters in a pattern must be adjacent in the permutation. In this paper we study the generating functions for the number of permutations on letters avoiding a generalized pattern $ab\mn c$ where , and containing a prescribed number of occurrences of generalized pattern $cd\mn e$ where . As a consequence, we derive all the previously known results for this kind of problems, as well as many new results.
19 pages