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

1, 1, 0, 0, 0, 0, 1, 8, 68, 480, 3637, 27968, 231410, 2014784, 18789010, 185234176, 1943243785, 21501237248, 251589065328, 3093350098432, 40007001803593, 541652523341824, 7679190979467688, 113578314941202432

Offset: 0

Author

R. J. Mathar, Oct 27 2014

Keywords

• nonn
• more

Crossrefs

Cf. A245377 (at least 2), A249391, A249392, A249393, A127697 (non-alternating).

Extensions

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

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

a(22)-a(23) from Max Alekseyev, Feb 20 2024