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 A177671 #5 Mar 02 2016 10:57:16 %S A177671 1,1,70,34650,63063000,304935162828,3227357965784040, %T A177671 65712161060921061615 %N A177671 Number of permutations of 4 copies of 1..n avoiding adjacent step pattern up, up, down, down, down, down. %Y A177671 Cf. A014608. %K A177671 nonn %O A177671 0,3 %A A177671 _R. H. Hardin_, May 10 2010