A177559 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down.

1, 6, 90, 2448, 105218, 6572088, 562874958, 63344668632, 9067009872984, 1608913338743280, 346665863545391736, 89160540714537206616, 26982910637581823115028, 9492077262717161359915632

Offset

1,2

Links

Table of n, a(n) for n=1..14.

Crossrefs

Sequence in context: A177580 A177587 A177585 * A177581 A177566 A177586

Adjacent sequences: A177556 A177557 A177558 * A177560 A177561 A177562

Keyword

nonn

Author

R. H. Hardin, May 10 2010

Extensions

a(11)-a(14) from Alois P. Heinz, Nov 02 2013

Status

approved