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A217805 Number of alternating permutations on 2n letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition). 0
1, 5, 42, 444, 5337, 69657, 962939, 13890083, 207042035 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..9.

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.

Sequence in context: A126765 A228793 A024492 * A217808 A151334 A005789

Adjacent sequences:  A217802 A217803 A217804 * A217806 A217807 A217808

KEYWORD

nonn,more,changed

AUTHOR

N. J. A. Sloane, Oct 12 2012

EXTENSIONS

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

STATUS

approved

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Last modified February 23 17:39 EST 2018. Contains 299584 sequences. (Running on oeis4.)