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A002218 Number of unlabeled nonseparable (or 2-connected) graphs (or blocks) with n nodes.
(Formerly M2873 N1155)
+0
7
0, 1, 1, 3, 10, 56, 468, 7123, 194066, 9743542, 900969091, 153620333545, 48432939150704, 28361824488394169, 30995890806033380784, 63501635429109597504951, 244852079292073376010411280, 1783160594069429925952824734641, 24603887051350945867492816663958981 (list; graph; listen)
OFFSET

1,4

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

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.

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 188.

R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.

R. W. Robinson, Enumeration of non-separable graphs, J. Combin. Theory 9 (1970), 327-356.

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1978.

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.

LINKS

R. W. Robinson, Table of n, a(n) for n = 1..26

R. W. Robinson, Tables

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), 289-308.

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Eric Weisstein's World of Mathematics, k-Connected Graph

CROSSREFS

Cf. A000088, A001349, A006289, A006290, A004115, A013922.

Sequence in context: A034234 A081721 A013009 this_sequence A107871 A111270 A112101

Adjacent sequences: A002215 A002216 A002217 this_sequence A002219 A002220 A002221

KEYWORD

nonn,easy,nice

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com).

EXTENSIONS

More terms from R. C. Read (rcread(AT)math.uwaterloo.ca). Robinson and Walsh list first 26 terms.

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Last modified December 16 17:18 EST 2009. Contains 170825 sequences.


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