Séminaire Lotharingien de Combinatoire, B34l (1995), 19
Kimmo Eriksson, Svante Linusson
The Size of Fulton's Essential Set
The essential set of a permutation was defined by Fulton as
the set of southeast corners of the diagram of the permutation.
In this paper we determine explicit formulas for the average size
of the essential set in the two cases of arbitrary permutations
and 321-avoiding permutations. Vexillary permutations
are discussed too.
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