A177565 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, down

1, 6, 90, 2520, 112920, 7398873, 667165914, 79232435816, 11987084051880, 2250732641346600

Offset

1,2

Links

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

Crossrefs

Sequence in context: A177284 A266735 A177564 * A177576 A177588 A177589

Adjacent sequences: A177562 A177563 A177564 * A177566 A177567 A177568

Keyword

nonn

Author

R. H. Hardin May 10 2010

Status

approved