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 A239368 #19 Jul 30 2014 08:16:28
%S A239368 1,1,4,27,252,3020,44220,765030,15269520,345376080,8730489600,
%T A239368 243911883600,7463164262400,248207881521600,8915064168410400,
%U A239368 343923449355486000,14182674669779616000,622591172035376544000,28986699477880400256000,1426677017904959524704000
%N A239368 Number of words of length n over the alphabet {0,...,n-1} that avoid the pattern 1111.
%H A239368 Alois P. Heinz, <a href="/A239368/b239368.txt">Table of n, a(n) for n = 0..350</a>
%F A239368 Recursion: see Maple program.
%p A239368 a:= proc(n) option remember; `if`(n<3, n^n,
%p A239368 ((105*n^3-252*n^2+175*n-36) *a(n-1) -2*(n-1)^2 *a(n-2)
%p A239368 +2*(5*n-2)*(n-1)^2*(n-2)^2*a(n-3)) / (4*(2*n-1)*(5*n-7)))
%p A239368 end:
%p A239368 seq(a(n), n=0..20); # _Alois P. Heinz_, Jul 20 2014
%Y A239368 Cf. A012244, A239295.
%K A239368 nonn
%O A239368 0,3
%A A239368 _Chad Brewbaker_, Mar 17 2014
%E A239368 a(8)-a(11) from _Alois P. Heinz_, Mar 17 2014
%E A239368 a(12)-a(19) from _Alois P. Heinz_, Jul 20 2014