A177293 Number of permutations of 3 copies of 1..n with all adjacent differences <= 3 in absolute value.

1, 1, 20, 1680, 369600, 37850400, 2626916040, 171548183912, 12520880883034, 920942694050320, 65368388837752640

Offset: 0

Author

R. H. Hardin, May 06 2010

Keywords

• nonn

Comments

a(n) = (3n)!/6^n for n<=4.

Crossrefs

Cf. A014606.

Extensions

a(10) from Alois P. Heinz, Jan 18 2016