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A177566
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up
0
1, 6, 90, 2478, 108087, 6858729, 597102395, 68327728061, 9947340852218, 1795593162877489
OFFSET
1,2
CROSSREFS
Sequence in context: A177585 A177559 A177581 * A177586 A177579 A177591
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved