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 A241156 #10 Feb 03 2016 10:20:16 %S A241156 1,1,2,7,22,82,308,1225,4954,20558,86572,369942,1598172,6972100, %T A241156 30663656,135826627,605386062,2713066882,12217967284,55262144418, %U A241156 250932354484,1143468874748,5227460728344,23968152050930,110191808568852,507857114699628 %N A241156 Number of complementary pairs of `homogenized' N-free graphs with n nodes. %H A241156 P. J. Cameron, <a href="http://dx.doi.org/10.1093/qmath/38.2.155">Some treelike objects</a>, Quart. J. Math. Oxford, 38 (1987), 155-183. See p. 166. %H A241156 Jacinta Covington, <a href="http://plms.oxfordjournals.org/content/s3-58/1/1.extract">A universal structure for N-free graphs</a>, Proc. London Math. Soc. (3) 58 (1989), no. 1, 1--16. MR0969544 (89m:03028). %F A241156 a(1)=1, thereafter a(n) = A226909(n)/2. %Y A241156 Cf. A226909. %K A241156 nonn %O A241156 1,3 %A A241156 _N. J. A. Sloane_, Apr 18 2014