login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Table of n, a(n) for n=0..15.

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

N. J. A. Sloane

EXTENSIONS

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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