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 A063688 #4 May 10 2013 12:44:50 %S A063688 1,1,3,10,39,164,746,3474,16658,81166,401169,2004517,10110757, %T A063688 51402250,263133142,1355126922,7016115632,36498130908,190673015083, %U A063688 999932115039,5262094054524,27779114013628,147072756065567,780722981065006 %N A063688 Number of 2-trees rooted at a triangle. %D A063688 F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 76, Eq. (3.5.13). %Y A063688 Cf. A005750, A058870, A058866, A054581. %K A063688 nonn %O A063688 1,3 %A A063688 _Vladeta Jovovic_, Aug 22 2001