A177286 Number of permutations of 2 copies of 1..n with all adjacent differences <= 5 in absolute value.

1, 6, 90, 2520, 113400, 7484400, 349272000, 12629539440, 394462558980, 11673071453460, 348672825749478

Offset

1,2

Comments

a(n)=(2n)!/2^n for n<=6

Links

Table of n, a(n) for n=1..11.

Crossrefs

Sequence in context: A177285 A177574 A177575 * A177594 A177287 A177288

Adjacent sequences: A177283 A177284 A177285 * A177287 A177288 A177289

Keyword

nonn

Author

R. H. Hardin May 06 2010

Status

approved