

A004102


Number of signed graphs with n nodes. Also number of 2multigraphs on n nodes.
(Formerly M2874)


17



1, 3, 10, 66, 792, 25506, 2302938, 591901884, 420784762014, 819833163057369, 4382639993148435207, 64588133532185722290294, 2638572375815762804156666529, 300400208094064113266621946833097
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OFFSET

1,2


COMMENTS

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


REFERENCES

F. Harary and R. W. Robinson, Exposition of the enumeration of pointlinesigned 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.
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 threecoloured 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 2subsets
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, 295308.
Vladeta Jovovic, Formulae for the number T(n,k) of nmultigraphs on k nodes
R. W. Robinson, Notes  "A Present for Neil Sloane"
R. W. Robinson, Notes  computer printout
R. W. Robinson & N. J. A. Sloane, Correspondence, 19701980


CROSSREFS

A column of A063841.
Sequence in context: A206724 A009400 A217388 * A072638 A262843 A080526
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



