%I A002218 M2873 N1155
%S A002218 0,1,1,3,10,56,468,7123,194066,9743542,900969091,153620333545,
%T A002218 48432939150704,28361824488394169,30995890806033380784,63501635429109597504951,
%U A002218 244852079292073376010411280,1783160594069429925952824734641,24603887051350945867492816663958981
%N A002218 Number of unlabeled nonseparable (or 2-connected) graphs (or blocks) 
               with n nodes.
%D A002218 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A002218 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002218 P. Butler and R. W. Robinson, On the computer calculation of the number 
               of nonseparable graphs, pp. 191 - 208 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 A002218 F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 
               1973, p. 188.
%D A002218 R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.
%D A002218 R. W. Robinson, Enumeration of non-separable graphs, J. Combin. Theory 
               9 (1970), 327-356.
%D A002218 R. W. Robinson, Numerical implementation of graph counting algorithms, 
               AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1978.
%D A002218 R. W. Robinson and T. R. S. Walsh, Inversion of cycle index sum relations 
               for 2- and 3-connected graphs. J. Combin. Theory Ser. B 57 (1993), 
               no. 2, 289-308.
%H A002218 R. W. Robinson, <a href="b002218.txt">Table of n, a(n) for n = 1..26</
               a>
%H A002218 R. W. Robinson, <a href="http://www.cs.uga.edu/~rwr/publications/tables.pdf">
               Tables</a>
%H A002218 R. W. Robinson and T. R. S. Walsh, <a href="http://www.cs.uga.edu/~rwr/
               publications/cycleindex.pdf">Inversion of cycle index sum relations 
               for 2- and 3-connected graphs</a>, J. Combin. Theory Ser. B. 57 (1993), 
               289-308.
%H A002218 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               BiconnectedGraph.html">Link to a section of The World of Mathematics.</
               a>
%H A002218 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               k-ConnectedGraph.html">k-Connected Graph</a>
%Y A002218 Cf. A000088, A001349, A006289, A006290, A004115, A013922.
%Y A002218 Sequence in context: A034234 A081721 A013009 this_sequence A107871 A111270 
               A112101
%Y A002218 Adjacent sequences: A002215 A002216 A002217 this_sequence A002219 A002220 
               A002221
%K A002218 nonn,easy,nice
%O A002218 1,4
%A A002218 N. J. A. Sloane (njas(AT)research.att.com).
%E A002218 More terms from R. C. Read (rcread(AT)math.uwaterloo.ca). Robinson and 
               Walsh list first 26 terms.