Séminaire Lotharingien de Combinatoire, B49a (2002), 11 pp.
Toufik Mansour and Julian West
Avoiding 2-letter Signed Patterns
Abstract.
Let Bn be the hyperoctahedral group, the set of all signed
permutations on n letters, and let Bn(T)
be the set of all
signed permutations in Bn which avoid a set T of signed
patterns. In this paper, we find all the cardinalities of the sets
Bn(T) where T \subseteq B2.
Some of the cardinalities
encountered involve inverse binomial coefficients, binomial
coefficients, Catalan numbers, and Fibonacci numbers.
Received: July 25, 2002.
Accepted: November 15, 2002.
Final version: December 3, 2002.
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