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A058642
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Number of unlabeled graphs with n edges, no nodes of degree 1 or 2, no multiple edges and no cut nodes, under "series-equivalence".
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2
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0, 0, 0, 0, 0, 1, 0, 1, 3, 5, 9
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,9
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COMMENTS
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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-.
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REFERENCES
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B. D. H. Tellegen, Geometrical configurations and duality of electrical networks, Philips Technical Review, 5 (1940), 324-330.
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LINKS
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EXAMPLE
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The first example, with 6 edges, is K_4. The second example has 8 edges and is the 1-skeleton of the square pyramid.
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CROSSREFS
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KEYWORD
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nonn,nice,more
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AUTHOR
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STATUS
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approved
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