A177580 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, up, down, up

1, 6, 90, 2432, 104088, 6469450, 551224281, 61682514624, 8774836958792, 1546903370655438

Offset

1,2

Links

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

Crossrefs

Sequence in context: A221097 A177584 A177558 * A177587 A177585 A177559

Adjacent sequences: A177577 A177578 A177579 * A177581 A177582 A177583

Keyword

nonn

Author

R. H. Hardin May 10 2010

Status

approved