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 A177606 #5 Jan 25 2016 15:53:21 %S A177606 1,1,20,1680,369600,167262000,135190246573,177591503329934, %T A177606 354324970027942152 %N A177606 Number of permutations of 3 copies of 1..n avoiding adjacent step pattern up, down, down, down, down. %Y A177606 Cf. A014606. %K A177606 nonn %O A177606 0,3 %A A177606 _R. H. Hardin_, May 10 2010