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A177560 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, up. 0
1, 6, 84, 2054, 78231, 4290094, 320821079, 31414709469, 3903342922319, 600255674485509, 111949642485388109, 24900064681761042208, 6512262064364063116565, 1978717544093002418592533 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..14.

CROSSREFS

Sequence in context: A147626 A123312 A010794 * A177562 A273935 A318399

Adjacent sequences:  A177557 A177558 A177559 * A177561 A177562 A177563

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 10 2010

EXTENSIONS

a(11)-a(14) from Alois P. Heinz, Nov 02 2013

STATUS

approved

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Last modified August 1 06:45 EDT 2021. Contains 346384 sequences. (Running on oeis4.)