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 A137861 #2 Mar 30 2012 18:49:09 %S A137861 1,1,2,5,18,78,522,6168,137352,6002584,509498932,82545585936, %T A137861 25251015686776,14527077828617744,15713242984902154384, %U A137861 32000507852263778595584,122967932076766466347469888 %N A137861 Number of unlabeled graphs with n nodes and an odd sum of nodes and edges. %C A137861 a(n) = A054960(n) for even n and A007869(n) for odd n. %Y A137861 Cf. A054960 Number of unlabeled graphs with n nodes and an odd number of edges. A007869 Complementary pairs of graphs on n nodes. Also unlabeled graphs with n nodes and an even number of edges. %K A137861 nonn %O A137861 1,3 %A A137861 _Tanya Khovanova_, Apr 29 2008