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A177581
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, up, up, down
0
1, 6, 90, 2466, 107556, 6834976, 596062132, 68333017226, 9966819746704, 1802533316442602
OFFSET
1,2
CROSSREFS
Sequence in context: A177587 A177585 A177559 * A177566 A177586 A177579
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved