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A005966 Number of trivalent planar loopless multigraphs with 2n nodes.
(Formerly M1511)
1
1, 2, 5, 17, 71, 357, 2143, 14960, 116560, 986983, 8874072 (list; graph; refs; listen; history; text; internal format)
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 * A082282 A005967 A104859

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

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Last modified July 12 22:46 EDT 2020. Contains 335669 sequences. (Running on oeis4.)