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 A177607 #5 Jan 25 2016 15:54:08 %S A177607 1,1,20,1680,359582,156245130,120386806922,150097348110878, %T A177607 283411248751268531 %N A177607 Number of permutations of 3 copies of 1..n avoiding adjacent step pattern up, down, down, down, up. %Y A177607 Cf. A014606. %K A177607 nonn %O A177607 0,3 %A A177607 _R. H. Hardin_, May 10 2010