A249390 - OEIS

%I #17 Feb 24 2024 00:49:10

%S 1,1,0,0,0,0,1,8,68,480,3637,27968,231410,2014784,18789010,185234176,

%T 1943243785,21501237248,251589065328,3093350098432,40007001803593,

%U 541652523341824,7679190979467688,113578314941202432

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

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

%K nonn,more

%O 0,8

%A _R. J. Mathar_, Oct 27 2014

%E a(17)-a(20) from _Alois P. Heinz_, Oct 27 2014

%E a(21) from _Alois P. Heinz_, Oct 28 2014

%E a(22)-a(23) from _Max Alekseyev_, Feb 20 2024