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 A063786 #3 May 10 2013 12:44:51 %S A063786 1,1,1,2,5,5,14,14,41,42,132,132,429,429,1428,1430,4862,4862,16796, %T A063786 16796,58781,58786,208012,208012,742900,742900,2674426,2674440, %U A063786 9694845,9694845,35357670,35357670,129644748,129644790,477638700,477638700 %N A063786 G.f.: A(x) = (x-2*x^2-2*x^3-(1+x)*sqrt(1-4*x^2)+sqrt(1-4*x^6))/(2*x^2). %D A063786 F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 78, (3.5.30). ( A(x) = s_1 bar (x) ). %Y A063786 Cf. A000108, A000207. %K A063786 nonn %O A063786 2,4 %A A063786 _Vladeta Jovovic_, Aug 24 2001