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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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) 12
 1, 2, 6, 26, 192, 3014, 127757, 16853750, 7343780765, 10733574184956, 52867617324773592, 882178116079222400788, 50227997322550920824045262, 9837048598740665027344331562224, 6681839615514161556535851222043192179, 15867777966020615016665849049841756464001994 (list; graph; refs; listen; history; text; internal format)
 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

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.

Last modified May 29 07:07 EDT 2023. Contains 363029 sequences. (Running on oeis4.)