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A177567 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, up, down 0
1, 6, 88, 2304, 95440, 5730914, 471168554, 50843909070, 6973120310921, 1184918837271686 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..10.

CROSSREFS

Sequence in context: A122770 A265267 A218260 * A177563 A177569 A327645

Adjacent sequences:  A177564 A177565 A177566 * A177568 A177569 A177570

KEYWORD

nonn

AUTHOR

R. H. Hardin May 10 2010

STATUS

approved

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Last modified March 30 09:22 EDT 2020. Contains 333125 sequences. (Running on oeis4.)