A177575 Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, down, down

1, 6, 90, 2520, 113400, 7480800, 680133100, 81515658984, 12453667803000, 2362332159735240

Offset

1,2

Links

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

Crossrefs

Sequence in context: A177589 A177285 A177574 * A177286 A177594 A177287

Adjacent sequences: A177572 A177573 A177574 * A177576 A177577 A177578

Keyword

nonn

Author

R. H. Hardin May 10 2010

Status

approved