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DM
1998

On numbers of Davenport-Schinzel sequences

13 years 10 months ago
On numbers of Davenport-Schinzel sequences
One class of Davenport-Schinzel sequences consists of finite sequences over n symbols without immediate repetitions and without any subsequence of the type abab. We present a bijective encoding of such sequences by rooted plane trees with distinguished nonleaves and we give a combinatorial proof of the formula 1 k − n + 1 2k − 2n k − n k − 1 2n − k − 1 for the number of such normalized sequences of length k. The formula was found by Gardy and Gouyou-Beauchamps by means of generating functions. We survey previous results concerning counting of DS sequences and mention several equivalent enumerative problems.
Martin Klazar
Added 22 Dec 2010
Updated 22 Dec 2010
Type Journal
Year 1998
Where DM
Authors Martin Klazar
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