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A004102 Number of signed graphs with n nodes. Also number of 2-multigraphs on n nodes.
(Formerly M2874)
11
1, 3, 10, 66, 792, 25506, 2302938, 591901884, 420784762014, 819833163057369, 4382639993148435207, 64588133532185722290294, 2638572375815762804156666529, 300400208094064113266621946833097 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A 2-multigraph is similar to an ordinary graph except there are 0, 1 or 2 edges between any two nodes (self-loops are not allowed).

REFERENCES

F. Harary and R. W. Robinson, Exposition of the enumeration of point-line-signed graphs, pp. 19 - 33 of Proc. Second Caribbean Conference Combinatorics and Computing (Bridgetown, 1977). Ed. R. C. Read and C. C. Cadogan. University of the West Indies, Cave Hill Campus, Barbados, 1977. vii+223 pp.

Harary, Frank; Palmer, Edgar M.; Robinson, Robert W.; Schwenk, Allen J.; Enumeration of graphs with signed points and lines. J. Graph Theory 1 (1977), no. 4, 295-308.

R. W. Robinson, personal communication.

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

R. W. Robinson, Table of n, a(n) for n = 1..22

J. Cummings, D. Kral, F. Pfender, K. Sperfeld et al., Monochromatic triangles in three-coloured graphs, Arxiv preprint arXiv:1206.1987. 2012. - From N. J. A. Sloane, Nov 25 2012

Harald Fripertinger, The cycle type of the induced action on 2-subsets

Vladeta Jovovic, Formulae for the number T(n,k) of n-multigraphs on k nodes

CROSSREFS

A row of A063841.

Sequence in context: A206724 A009400 A217388 * A072638 A080526 A232213

Adjacent sequences:  A004099 A004100 A004101 * A004103 A004104 A004105

KEYWORD

nonn,nice,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Vladeta Jovovic, Jan 06 2000

STATUS

approved

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Last modified September 2 05:25 EDT 2014. Contains 246322 sequences.