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 A026578 #4 Mar 30 2012 18:56:09 %S A026578 1,3,13,60,225,1148,4235,22296,82425,440308,1634435,8809736,32819839, %T A026578 178029138,665162897,3625521728,13577768505 %N A026578 T(2n-1,n-2), T given by A026568. %K A026578 nonn %O A026578 2,2 %A A026578 _Clark Kimberling_