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Search: id:A058668
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| A058668 |
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Number of unlabeled graphs with n edges, no nodes of degree 1 and no cut nodes, under "series-equivalence"; multiple edges are allowed. |
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+0
3
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OFFSET
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1,3
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COMMENT
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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-.
Start with the graph consisting of a single edge together with the graphs described in A058642; apply the operations of replacing edges by two edges in series or parallel; discard equivalent graphs; the result is A058668.
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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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CROSSREFS
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Cf. A058642.
Sequence in context: A087128 A154365 A029544 this_sequence A092790 A105043 A083095
Adjacent sequences: A058665 A058666 A058667 this_sequence A058669 A058670 A058671
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KEYWORD
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nonn,nice,more
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Dec 30 2000
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