%I A000421
%S A000421 1,2,6,20,91,509,3608,31856,340416,4269971,61133757,978098997
%N A000421 Number of isomorphism classes of connected 3-regular loopless multigraphs 
               of order 2n.
%D A000421 A. T. Balaban, Enumeration of Cyclic Graphs, pp. 63-105 of A. T. Balaban, 
               ed., Chemical Applications of Graph Theory, Ac. Press, 1976; see 
               p. 92.
%D A000421 CRC Handbook of Combinatorial Designs, 1996, p. 651.
%D A000421 Brendan McKay, software at http://cs.anu.edu.au/~bdm/nauty/
%Y A000421 Cf. A129416, A005967, A129417, A129419, A129421, A129423, A129425
%Y A000421 Sequence in context: A027321 A027315 A005965 this_sequence A009244 A104985 
               A079575
%Y A000421 Adjacent sequences: A000418 A000419 A000420 this_sequence A000422 A000423 
               A000424
%K A000421 nonn
%O A000421 1,2
%A A000421 N. J. A. Sloane (njas(AT)research.att.com).
%E A000421 More terms from Brendan McKay (bdm(at)cs.anu.edu.au), Apr 15 2007