%I A005638 M1656
%S A005638 1,2,6,21,94,540,4207,42110,516344,7373924,118573592,2103205738,
%T A005638 40634185402,847871397424,18987149095005,454032821688754,
%U A005638 11544329612485981,310964453836198311,8845303172513781271
%N A005638 Number of unlabeled trivalent (or cubic) graphs with 2n nodes.
%C A005638 Because the triangle A051031 is symmetric, a(n) is also the number of 
               (2n-4)-regular graphs on 2n vertices. [From Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), 
               Sep 22 2009]
%D A005638 Brinkmann, G. "Fast Generation of Cubic Graphs." J. Graph Th. 23, 139-149, 
               1996.
%D A005638 R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.
%D A005638 Robinson, R. W.; Wormald, N. C.; Numbers of cubic graphs. J. Graph Theory 
               7 (1983), no. 4, 463-467.
%D A005638 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A005638 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               CubicGraph.html">Link to a section of The World of Mathematics.</
               a>
%Y A005638 Cf. A002851, A000421.
%Y A005638 Regular graphs A005176 (any degree), A051031 (triangular array), chosen 
               degrees: A000012 (k=0), A059841 (k=1), A008483 (k=2), A005638 (k=3), 
               A033301 (k=4), A165626 (k=5), A165627 (k=6), A165628 (k=7). [From 
               Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Nov 07 2009]
%Y A005638 Sequence in context: A147719 A115089 A001928 this_sequence A008988 A061232 
               A020091
%Y A005638 Adjacent sequences: A005635 A005636 A005637 this_sequence A005639 A005640 
               A005641
%K A005638 nonn,nice
%O A005638 2,2
%A A005638 N. J. A. Sloane (njas(AT)research.att.com).
%E A005638 More terms from R. C. Read (rcread(AT)math.uwaterloo.ca).