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.

1, 1, 3, 14, 115, 2086, 101791, 14835870, 6852422567, 10338780759514, 51804974736769271, 872530598196790164797, 49930445153769776449253479, 9805619466642079028742952893709, 6670375074613812276139335045628924297, 15853216549413764390038207575938343994222273

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

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]

Crossrefs

Row sums of A123547.

Cf. A007139, A054976, A319155.

Formula

a(n) = (A054976(n) + A319155(n)) / 2. - Andrew Howroyd, Sep 25 2018

Extensions

a(11)-a(15) from Andrew Howroyd, Sep 25 2018