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 A177617 #5 Mar 02 2016 11:01:03 %S A177617 1,1,20,1680,369600,167510862,135702841152,178756061502340, %T A177617 357729925926146006 %N A177617 Number of permutations of 3 copies of 1..n avoiding adjacent step pattern up, down, down, down, down, up. %Y A177617 Cf. A014606. %K A177617 nonn %O A177617 0,3 %A A177617 _R. H. Hardin_, May 10 2010