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 A239375 #11 Dec 03 2023 17:24:11
%S A239375 1,1,4,27,250,2915,40766,662494,12236190,252664815,5759288044,
%T A239375 143463453199,3873471153366,112587628893480
%N A239375 Number of words of length n over the alphabet {0, ..., n-1} that avoid the pattern 1221.
%Y A239375 Cf. A239295.
%K A239375 nonn,more
%O A239375 0,3
%A A239375 _Chad Brewbaker_, Mar 17 2014
%E A239375 a(8)-a(13) from _Martin Ehrenstein_, Dec 03 2023