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 A058387 Number of series-parallel networks with n unlabeled edges, multiple edges not allowed. 3
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS 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. REFERENCES J. W. Moon, Some enumerative results on series-parallel networks, Annals Discrete Math., 33 (1987), 199-226 (the sequence v_n). LINKS S. R. Finch, Series-parallel networks S. R. Finch, Series-parallel networks, July 7, 2003. [Cached copy, with permission of the author] FORMULA A058387 = A058385 + A058386. CROSSREFS 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 KEYWORD nonn,nice,easy AUTHOR N. J. A. Sloane, Dec 20 2000 STATUS approved

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Last modified February 27 21:59 EST 2020. Contains 332312 sequences. (Running on oeis4.)