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 A177657 #5 Mar 02 2016 10:55:13 %S A177657 1,1,70,34650,63063000,305540235000,3244612572406800, %T A177657 66346172137847738628 %N A177657 Number of permutations of 4 copies of 1..n avoiding adjacent step pattern up, down, down, down, down, down. %Y A177657 Cf. A014608. %K A177657 nonn %O A177657 0,3 %A A177657 _R. H. Hardin_, May 10 2010