A177577 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up, down

1, 6, 90, 2502, 110892, 7173916, 637847566, 74626447992, 11115748465934, 2053937512504320

Offset

1,2

Links

Table of n, a(n) for n=1..10.

Crossrefs

Sequence in context: A177591 A177571 A177590 * A177572 A177583 A177578

Adjacent sequences: A177574 A177575 A177576 * A177578 A177579 A177580

Keyword

nonn

Author

R. H. Hardin May 10 2010

Status

approved