A177561 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, down

1, 6, 74, 1730, 62340, 3258982, 232475188, 21711360018, 2576183815724, 378267268113542

Offset

1,2

Links

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

Crossrefs

Sequence in context: A317344 A357011 A231691 * A269334 A069852 A266574

Adjacent sequences: A177558 A177559 A177560 * A177562 A177563 A177564

Keyword

nonn

Author

R. H. Hardin May 10 2010

Status

approved