Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #10 Mar 02 2021 04:53:07
%S 1,1,3,12,79,1123,42065,4880753,1674021742,1612191702946,
%T 4291399235883144,31570649902282023158,644451747846907273827686,
%U 36675914469877423648734408329,5846124500387959287169919356171145
%N Number of connected switching classes of signed graphs with n nodes.
%C Also, number of unlabeled connected strength 2 Eulerian graphs with n nodes. - _Vladeta Jovovic_, Mar 14 2009
%D Bussemaker, F. C.; Cameron, P. J.; Seidel, J. J.; and Tsaranov, S. V., Tables of signed graphs, Report-WSK 91-01, Eindhoven University of Technology, Department of Mathematics and Computing Science, Eindhoven, 1991, 105 pp. MR: 92g:05001.
%H F. C. Bussemaker, P. J. Cameron, J. J. Seidel, and S. V. Tsaranov, <a href="https://www.researchgate.net/publication/241872284_Tables_of_signed_graphs ">Tables of signed graphs</a>, Report-WSK 91-01, Eindhoven University of Technology, Department of Mathematics and Computing Science, Eindhoven, 1991, 105 pp. (MR: 92g:05001).
%Y Cf. A007127, A053465.
%K nonn
%O 1,3
%A _N. J. A. Sloane_, Jul 16 2003
%E Edited by _N. J. A. Sloane_ Apr 05 2009 at the suggestion of Vladeta Jovovic