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A177577
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up, down
0
1, 6, 90, 2502, 110892, 7173916, 637847566, 74626447992, 11115748465934, 2053937512504320
OFFSET
1,2
CROSSREFS
Sequence in context: A177591 A177571 A177590 * A177572 A177583 A177578
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved