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 A007140 Number of unlabeled bicolored graphs, with no isolated nodes, on 2n nodes having n nodes of each color and allowing the color classes to be interchanged. (Formerly M2980) 5
 1, 1, 3, 14, 115, 2086, 101791, 14835870, 6852422567, 10338780759514, 51804974736769271, 872530598196790164797, 49930445153769776449253479, 9805619466642079028742952893709, 6670375074613812276139335045628924297, 15853216549413764390038207575938343994222273 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS F. Harary, L. March and R. W. Robinson, On enumerating certain design problems in terms of bicolored graphs with no isolates, Environment and Planning, B 5 (1978), 31-43. F. Harary, L. March and R. W. Robinson, On enumerating certain design problems in terms of bicolored graphs with no isolates, Environment and Planning B: Urban Analytics and City Science, 5 (1978), 31-43. [Annotated scanned copy] FORMULA a(n) = (A054976(n) + A319155(n)) / 2. - Andrew Howroyd, Sep 25 2018 CROSSREFS Row sums of A123547. Cf. A007139, A054976, A319155. Sequence in context: A180435 A256159 A122081 * A161936 A304983 A349013 Adjacent sequences:  A007137 A007138 A007139 * A007141 A007142 A007143 KEYWORD nonn AUTHOR EXTENSIONS a(11)-a(15) from Andrew Howroyd, Sep 25 2018 STATUS approved

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Last modified August 17 15:14 EDT 2022. Contains 356189 sequences. (Running on oeis4.)