A217805 Number of alternating permutations on 2n letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition).
1, 5, 42, 444, 5337, 69657, 962939, 13890083, 207042035
Offset: 1
Links
- J. B. Lewis, Pattern Avoidance for Alternating Permutations and Reading Words of Tableaux, Ph. D. Dissertation, Department of Mathematics, MIT, 2012.
Extensions
a(7)-a(9) from Lars Blomberg, Feb 17 2018