Abstract
Recently, Stanley [Longest alternating subsequences of permutations, preprint, arXiv/0511419v1] studied the length of the longest alternating subsequence of a permutation in the symmetric group, where a sequence a, b, c, d, ... is alternating if a > b < c > d < ⋯. In this paper, we extend this result to the case of k-ary words. More precisely, we find an explicit formula for the generating function of the number of k-ary words of length n according to the length of the longest alternating subsequence.
Original language | English |
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Pages (from-to) | 119-124 |
Number of pages | 6 |
Journal | Discrete Applied Mathematics |
Volume | 156 |
Issue number | 1 |
DOIs | |
State | Published - 1 Jan 2008 |
Keywords
- Alternating sequence
- Generating function
- k-Ary word
ASJC Scopus subject areas
- Discrete Mathematics and Combinatorics
- Applied Mathematics