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A177575
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, down, down
0
1, 6, 90, 2520, 113400, 7480800, 680133100, 81515658984, 12453667803000, 2362332159735240
OFFSET
1,2
CROSSREFS
Sequence in context: A177589 A177285 A177574 * A177286 A177594 A177287
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved