A217806 Number of alternating permutations on 2n letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition).

1, 4, 28, 260, 2844, 34564, 451868, 6231556, 89510428

Offset: 1

Author

N. J. A. Sloane, Oct 12 2012

Keywords

• nonn
• more

Links

• J. B. Lewis, Pattern Avoidance for Alternating Permutations and Reading Words of Tableaux, Ph. D. Dissertation, Department of Mathematics, MIT, 2012.

Crossrefs

Cf. A181197, A217799-A217830.

Extensions

a(7)-a(9) from Lars Blomberg, Feb 17 2018