%I #4 Mar 30 2012 16:48:56
%S 0,0,0,0,0,1,0,1,3,5,9
%N Number of unlabeled graphs with n edges, no nodes of degree 1 or 2, no multiple edges and no cut nodes, under "series-equivalence".
%C Under "series-equivalence" two graphs are equivalent if one can be obtained from the other by exchanging two subgraphs in series: replacing -A-B- by -B-A-.
%D B. D. H. Tellegen, Geometrical configurations and duality of electrical networks, Philips Technical Review, 5 (1940), 324-330.
%e The first example, with 6 edges, is K_4. The second example has 8 edges and is the 1-skeleton of the square pyramid.
%Y Cf. A058668.
%K nonn,nice,more
%O 1,9
%A _N. J. A. Sloane_, Dec 30 2000