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 A094538 #4 Mar 30 2012 16:49:56 %S A094538 0,0,3,9,33,99,315,945,2883,8649,26091,78273,235233,705699,2118339, %T A094538 6355017,19068729,57206187,171629595,514888785,1544699313,4634097939, %U A094538 13902392691,41707178073,125121830427,375365491281 %N A094538 Number of ternary words of length n that are not "bifix-free". %F A094538 Equals 3^n - A019308(n). %Y A094538 See A019308 and A003000 for much more information. Cf. A094539. %K A094538 nonn,easy %O A094538 0,3 %A A094538 _N. J. A. Sloane_, Jun 06 2004