A331013 - OEIS

A331013

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 edges having two colors and allowing the node color classes to be interchanged. Edge colors are swappable (permuted by the symmetric group).

1, 4, 13, 104, 1507, 64203, 8426875, 3671999389, 5366787092478, 26433809041087192, 441089058039611200394, 25113998661290096278734134, 4918524299370332513672165781112, 3340919807757080784843712707230030713, 7933888983010307508332924524920878232000997, 66370395190630232518212377765981306426650525779505

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Color swaps of the node colors are reflections of the biclique about a vertical axis, with one part on the left and the other on the right. Edge colors are distinct from the two node colors.

REFERENCES

E. Palmer and F. Harary, Graphical Enumeration, Academic Press, 1973.

LINKS

Table of n, a(n) for n=1..16.

Marko Riedel, Math.StackExchange, Counting bicliques

Marko Riedel, Cycle indices for K_{n,n} including shuffles and reflections as well as Power Group Enumeration implementation.

CROSSREFS

Cf. A007139, A331014.

Sequence in context: A058014 A290392 A261785 * A362283 A276912 A045886

Adjacent sequences: A331010 A331011 A331012 * A331014 A331015 A331016

KEYWORD

nonn

AUTHOR

Marko Riedel, Jan 06 2020

STATUS

approved