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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
OFFSET
1,2
CROSSREFS
Sequence in context: A007152 A345248 A295258 * A316212 A337592 A192485
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 10 2010
EXTENSIONS
a(12)-a(15) from Alois P. Heinz, Oct 22 2013
STATUS
approved