A179981 Number of permutations of 1..n with the difference of the k-th adjacent pair no greater than k, k=1..n-1.

2, 4, 10, 26, 82, 294, 1210, 5642, 29658, 171302, 1082098, 7427510, 54982606, 436014046, 3689906314, 33184698742, 316299334442, 3183340138774, 33735799824070

Offset

2,1

Links

Table of n, a(n) for n=2..20.

Example

For n=3, the four solutions are (1,2,3), (2,1,3), (2,3,1), (3,2,1).

Crossrefs

Sequence in context: A135410 A148103 A148104 * A086991 A272603 A272602

Adjacent sequences: A179978 A179979 A179980 * A179982 A179983 A179984

Keyword

nonn

Author

R. H. Hardin, Aug 04 2010

Status

approved