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A177586
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, up, down, down
0
1, 6, 90, 2478, 108636, 6939540, 608630577, 70186000080, 10298227034520, 1873626436312246
OFFSET
1,2
CROSSREFS
Sequence in context: A177559 A177581 A177566 * A177579 A177591 A177571
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved