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A177562 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, up 0
1, 6, 84, 2123, 84034, 4804627, 375435365, 38463186965, 5004563283887, 806386210926308 (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: A123312 A010794 A177560 * A273935 A318399 A171200

Adjacent sequences:  A177559 A177560 A177561 * A177563 A177564 A177565

KEYWORD

nonn

AUTHOR

R. H. Hardin May 10 2010

STATUS

approved

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Last modified July 24 21:47 EDT 2021. Contains 346273 sequences. (Running on oeis4.)