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 A217826 #8 Oct 08 2018 09:30:38
%S A217826 1,19,887,66816,6795966,850144907
%N A217826 Number of permutations of length 3n with descent set {3, 6, ...} that avoid a certain pattern of length 4 or 5 (see Lewis, 2012, Appendix, for precise definition).
%H A217826 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 A217826 Cf. A181197, A217799-A217830.
%K A217826 nonn,more
%O A217826 1,2
%A A217826 _N. J. A. Sloane_, Oct 13 2012
%E A217826 a(5)-a(6) from _Lars Blomberg_, Mar 09 2018