%I A004102 M2874
%S A004102 1,3,10,66,792,25506,2302938,591901884,420784762014,819833163057369,
%T A004102 4382639993148435207,64588133532185722290294,
%U A004102 2638572375815762804156666529,300400208094064113266621946833097
%N A004102 Number of signed graphs with n nodes. Also number of 2-multigraphs on 
               n nodes.
%C A004102 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).
%D A004102 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A004102 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.
%D A004102 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.
%D A004102 R. W. Robinson, personal communication.
%D A004102 R. W. Robinson, Numerical implementation of graph counting algorithms, 
               AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.
%H A004102 R. W. Robinson, <a href="b004102.txt">Table of n, a(n) for n = 1..22</
               a>
%H A004102 Harald Fripertinger, <a href="http://www.mathe2.uni-bayreuth.de/frib/
               html/book/hyl00_42.html">The cycle type of the induced action on 
               2-subsets</a>
%H A004102 Vladeta Jovovic, <a href="a063843.rtf">Formulae for the number T(n,k) 
               of n-multigraphs on k nodes</a>
%Y A004102 A row of A063841.
%Y A004102 Sequence in context: A042705 A041014 A009400 this_sequence A072638 A080526 
               A143083
%Y A004102 Adjacent sequences: A004099 A004100 A004101 this_sequence A004103 A004104 
               A004105
%K A004102 nonn,nice,easy
%O A004102 1,2
%A A004102 N. J. A. Sloane (njas(AT)research.att.com).
%E A004102 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 06 2000