A177566 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up

1, 6, 90, 2478, 108087, 6858729, 597102395, 68327728061, 9947340852218, 1795593162877489

Offset

1,2

Links

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

Crossrefs

Sequence in context: A177585 A177559 A177581 * A177586 A177579 A177591

Adjacent sequences: A177563 A177564 A177565 * A177567 A177568 A177569

Keyword

nonn

Author

R. H. Hardin May 10 2010

Status

approved