This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A249393 #14 Mar 09 2024 09:52:57 %S A249393 1,1,0,0,0,0,0,0,0,0,0,0,1,64,4352,103680,2644488,48052224,922764744, %T A249393 15466088448,271484691944,4512300607488,78169637107873, %U A249393 1332149989277696,23596090882390538 %N A249393 The number of down-up permutations of [n] where adjacent elements differ by at least 6. %Y A249393 Cf. A245377 (stride >=2), A249390, A249391, A249392, A179959 (non-alternating). %K A249393 nonn,more %O A249393 0,14 %A A249393 _R. J. Mathar_, Oct 27 2014 %E A249393 a(19)-a(20) from _Alois P. Heinz_, Oct 27 2014 %E A249393 a(21) from _Alois P. Heinz_, Oct 29 2014 %E A249393 a(22)-a(24) from _Max Alekseyev_, Mar 09 2024