Olivier Guibert

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Vexillary permutations are very important for the study of Schubert polynomials which are involved in several areas of mathematics and physics. In this note we determine the number of n-length vexillary involutions, that is 2143-avoiding involutions, which are equal to their mirror=complement by establishing a bijection with n-length left factors of Motzkin(More)
We examine the sets of permutations that are sorted by two passes through a stack with a D8 operation performed in between. From a characterization of these in terms of generalized excluded patterns, we prove two conjectures on their enumeration, that can be refined with the distribution of some statistics. The results are obtained by generating trees.(More)
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