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 A177647 #5 Mar 02 2016 10:52:26 %S A177647 1,1,70,34650,63063000,303526299000,3187068420047305, %T A177647 64239844119903312514 %N A177647 Number of permutations of 4 copies of 1..n avoiding adjacent step pattern up, down, down, down, down. %Y A177647 Cf. A014608. %K A177647 nonn %O A177647 0,3 %A A177647 _R. H. Hardin_, May 10 2010