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 A239377 #9 Mar 19 2014 13:03:41
%S A239377 1,1,4,27,252,2935,40336,632870
%N A239377 Words of length n over the alphabet {0,...,n-1} that avoid the pattern 1231.
%Y A239377 Cf. A239295.
%K A239377 nonn,more
%O A239377 0,3
%A A239377 _Chad Brewbaker_, Mar 17 2014