A177562 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, up

1, 6, 84, 2123, 84034, 4804627, 375435365, 38463186965, 5004563283887, 806386210926308

Offset

1,2

Links

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

Crossrefs

Sequence in context: A123312 A010794 A177560 * A273935 A318399 A171200

Adjacent sequences: A177559 A177560 A177561 * A177563 A177564 A177565

Keyword

nonn

Author

R. H. Hardin May 10 2010

Status

approved