A005966 Number of trivalent planar loopless multigraphs with 2n nodes. (Formerly M1511)

1, 2, 5, 17, 71, 357, 2143, 14960, 116560, 986983, 8874072

Offset

1,2

References

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.

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

Links

Table of n, a(n) for n=1..11.

Prog

(nauty/bash) for n in {1..10}; do geng -cqD3 $[2*$n] | planarg -q | multig -ur3; done # Sean A. Irvine, Oct 25 2016

Crossrefs

Cf. A000421 (allowing non-planar), A005957 (allowing loops).

Sequence in context: A057219 A084869 A101900 * A336282 A082282 A005967

Adjacent sequences: A005963 A005964 A005965 * A005967 A005968 A005969

Keyword

nonn,more

Author

N. J. A. Sloane.

Extensions

a(7)-a(11) and title improved by Sean A. Irvine, Oct 25 2016

Status

approved