A170808 Number of permutations of 1..n with all differences of elements separated by distances 1 or 2 being respectively unique.

1, 2, 4, 12, 40, 116, 252, 768, 2704, 12756, 63168, 338308, 1956876, 11971780, 77909884, 535178056, 3906154920, 30146769464, 244980749052, 2094507398508

Offset: 1

Author

R. H. Hardin Dec 02 2009

Keywords

• nonn

Comments

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