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 A217799 #15 Nov 22 2023 04:21:36 %S A217799 1,2,16,168,2112,30030,466752,7759752,135980416 %N A217799 Number of alternating permutations on 2n+1 letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition). %C A217799 Probably the same as A123555 for n>0. - _R. J. Mathar_, Nov 22 2023 %H A217799 J. B. Lewis, <a href="https://dspace.mit.edu/handle/1721.1/73444">Pattern Avoidance for Alternating Permutations and Reading Words of Tableaux</a>, Ph. D. Dissertation, Department of Mathematics, MIT, 2012. %Y A217799 Cf. A181197, A217799-A217830. %K A217799 nonn,more %O A217799 0,2 %A A217799 _N. J. A. Sloane_, Oct 12 2012 %E A217799 a(6)-a(8) from _Lars Blomberg_, Jan 23 2018