A007139 Number of unlabeled bicolored bipartite graphs on 2n nodes having n nodes of each color with no edges between vertices of the same color and allowing the color classes to be interchanged. (Formerly M4172)

1, 2, 6, 26, 192, 3014, 127757, 16853750, 7343780765, 10733574184956, 52867617324773592, 882178116079222400788, 50227997322550920824045262, 9837048598740665027344331562224, 6681839615514161556535851222043192179, 15867777966020615016665849049841756464001994

Offset

0,2

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

Marko Riedel, Table of n, a(n) for n = 0..30

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]

Marko Riedel, Cycle indices for K_{n,n} including shuffles and reflections.

Marko Riedel, Maple code for cycle indices of K_{n,n}

Formula

a(n) = (A002724(n)+A122082(n))/2. - Vladeta Jovovic, Feb 27 2007

Crossrefs

Cf. A007140.

Sequence in context: A211604 A032014 A112948 * A306147 A331937 A162438

Adjacent sequences: A007136 A007137 A007138 * A007140 A007141 A007142

Keyword

nonn

Author

N. J. A. Sloane

Extensions

More terms from Vladeta Jovovic, Feb 27 2007

Edited by N. J. A. Sloane, Aug 14 2007

Name clarified by Marko Riedel, Jun 15 2017

More terms from Marko Riedel, Jun 16 2017

Status

approved