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A058387
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Number of series-parallel networks with n unlabeled edges, multiple edges not allowed.
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3
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0, 1, 1, 2, 4, 8, 18, 40, 94, 224, 548, 1356, 3418, 8692, 22352, 57932, 151312, 397628, 1050992, 2791516, 7447972, 19950628, 53635310, 144664640, 391358274, 1061628772, 2887113478, 7869761108, 21497678430, 58841838912, 161356288874
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OFFSET
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0,4
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COMMENTS
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This is a series-parallel network: o-o; all other series-parallel networks are obtained by connecting two series-parallel networks in series or in parallel. See A000084 for examples.
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REFERENCES
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J. W. Moon, Some enumerative results on series-parallel networks, Annals Discrete Math., 33 (1987), 199-226 (the sequence v_n).
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LINKS
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Table of n, a(n) for n=0..30.
Index entries for sequences mentioned in Moon (1987)
S. R. Finch, Series-parallel networks
S. R. Finch, Series-parallel networks, July 7, 2003. [Cached copy, with permission of the author]
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FORMULA
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A058387 = A058385 + A058386.
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CROSSREFS
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Cf. A058379, A058386, A058385, A000084, A000311, A000669, A006351.
Sequence in context: A000967 A288309 A096813 * A330052 A317787 A019231
Adjacent sequences: A058384 A058385 A058386 * A058388 A058389 A058390
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane, Dec 20 2000
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STATUS
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approved
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