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 A058642 #4 Mar 30 2012 16:48:56 %S A058642 0,0,0,0,0,1,0,1,3,5,9 %N A058642 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 A058642 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 A058642 B. D. H. Tellegen, Geometrical configurations and duality of electrical networks, Philips Technical Review, 5 (1940), 324-330. %e A058642 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 A058642 Cf. A058668. %K A058642 nonn,nice,more %O A058642 1,9 %A A058642 _N. J. A. Sloane_, Dec 30 2000