A170809 Number of permutations of 1..n with all differences of elements separated by distances 1 through 3 being respectively unique.

1, 2, 4, 12, 40, 116, 200, 444, 864, 3368, 10936, 38320, 139848, 534828, 2230464, 9802612, 46188544, 231210272, 1213437504, 6717614708, 39002297800

Offset

1,2

Comments

(Empirical) Equals A008404 for n<=2m+2, where m is the maximum difference separation 3.

Links

Table of n, a(n) for n=1..21.

Crossrefs

Sequence in context: A170812 A170811 A170810 * A170808 A366579 A099214

Adjacent sequences: A170806 A170807 A170808 * A170810 A170811 A170812

Keyword

nonn

Author

R. H. Hardin Dec 02 2009

Status

approved