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A177554 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down. 0
1, 4, 28, 304, 4576, 91072, 2306176, 71993344, 2707268608, 120392433664, 6235322515456, 371376015818752, 25166910597922816, 1922787147517394944, 164313634414773403648 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..15.

CROSSREFS

Sequence in context: A274043 A007152 A295258 * A316212 A192485 A332097

Adjacent sequences:  A177551 A177552 A177553 * A177555 A177556 A177557

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 10 2010

EXTENSIONS

a(12)-a(15) from Alois P. Heinz, Oct 22 2013

STATUS

approved

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Last modified July 4 15:43 EDT 2020. Contains 335448 sequences. (Running on oeis4.)