A249390 The number of down-up permutations of [n] where adjacent elements differ at least by 3.

1, 1, 0, 0, 0, 0, 1, 8, 68, 480, 3637, 27968, 231410, 2014784, 18789010, 185234176, 1943243785, 21501237248, 251589065328, 3093350098432, 40007001803593, 541652523341824

Offset

0,8

Links

Table of n, a(n) for n=0..21.

Crossrefs

Cf. A245377 (at least 2), A249391 - A249393, A127697 (non-alternating).

Sequence in context: A208947 A296670 A263477 * A190510 A282563 A163307

Adjacent sequences: A249387 A249388 A249389 * A249391 A249392 A249393

Keyword

nonn,more

Author

R. J. Mathar, Oct 27 2014

Extensions

a(17)-a(20) from Alois P. Heinz, Oct 27 2014

a(21) from Alois P. Heinz, Oct 28 2014

Status

approved