A177288 Number of permutations of 2 copies of 1..n with all adjacent differences <= 7 in absolute value.

1, 1, 6, 90, 2520, 113400, 7484400, 681080400, 81729648000, 7580424852000, 569159625434400, 36636506215016400, 2141931687266957040

Offset

0,3

Links

Table of n, a(n) for n=0..12.

Formula

a(n) = (2n)!/2^n for n<=8.

Crossrefs

Cf. A000680.

Sequence in context: A177286 A177594 A177287 * A177289 A177290 A000680

Adjacent sequences: A177285 A177286 A177287 * A177289 A177290 A177291

Keyword

nonn,more

Author

R. H. Hardin, May 06 2010

Extensions

a(0), a(12) from Alois P. Heinz, May 30 2025

Status

approved