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Enumeration of 3-letter patterns in compositions

S. Heubach·T. Mansour
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Abstract

Let A be any set of positive integers and n a positive integer. A composition of n with parts in A is an ordered collection of one or more elements in A whose sum is n. We derive generating functions for the number of compositions of n with m parts in A that have r occurrences of 3-letter patterns formed by two (adjacent) instances of levels, rises and drops. We also derive asymptotics for the number of compositions of n that avoid a given pattern. Finally, we obtain the generating function for the number of k-ary words of length m which contain a prescribed number of occurrences of a given pattern as a special case of our results.

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S. Heubach, T. Mansour. 2006-03-13. Enumeration of 3-letter patterns in compositions. https://arxiv.org/abs/math/0603285

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