Restricted 132-alternating permutations and Chebyshev polynomials
Abstract
A permutation is said to be \emph{alternating} if it starts with rise and then descents and rises come in turn. In this paper we study the generating function for the number of alternating permutations on $n$ letters that avoid or contain exactly once 132 and also avoid or contain exactly once an arbitrary pattern on $k$ letters. In several interesting cases the generating function depends only on $k$ and is expressed via Chebyshev polynomials of the second kind.
- Publication:
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arXiv Mathematics e-prints
- Pub Date:
- October 2002
- DOI:
- arXiv:
- arXiv:math/0210058
- Bibcode:
- 2002math.....10058M
- Keywords:
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- Combinatorics
- E-Print:
- 22 pages