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 A177630 #9 Mar 02 2016 11:01:28 %S A177630 1,1,20,1680,369600,167895912,136567215720,180834782762247, %T A177630 364064983677371040 %N A177630 Number of permutations of 3 copies of 1..n avoiding adjacent step pattern up, up, down, down, down, down. %Y A177630 Cf. A014606. %K A177630 nonn,more %O A177630 0,3 %A A177630 _R. H. Hardin_, May 10 2010