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 A223905 #36 Nov 29 2019 11:58:20 %S A223905 1,1,2,6,24,120,717,4824,34629,256689,1935301 %N A223905 Number of 4-vexillary permutations in S_n, that is, permutations whose Stanley symmetric function has at most 4 terms or at most 4 Edelman-Greene tableaux. %C A223905 This family is characterized by a finite set of patterns. %H A223905 S. Billey and B. Pawlowski, <a href="https://arxiv.org/abs/1304.7870">Permutation Patterns, Stanley symmetric functions and generalized Specht modules</a>, arXiv:1304.7870 [math.CO], 2013. %H A223905 Elizabeth Hartung, Hung Phuc Hoang, Torsten Mütze, Aaron Williams, <a href="https://arxiv.org/abs/1906.06069">Combinatorial generation via permutation languages. I. Fundamentals</a>, arXiv:1906.06069 [cs.DM], 2019. %Y A223905 Cf. A005802, A224318. %K A223905 nonn,more %O A223905 0,3 %A A223905 _Sara Billey_, Apr 04 2013 %E A223905 a(0)=1 prepended by _Alois P. Heinz_, Jul 31 2019