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A177578
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up, up
0
1, 6, 90, 2510, 111924, 7292080, 653417953, 77078901216, 11579203589017, 2158323961477372
OFFSET
1,2
CROSSREFS
Sequence in context: A177577 A177572 A177583 * A177582 A177592 A177593
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved