A005028 Number of symmetric trivalent maps with n nodes.

1, 2, 4, 12, 33, 102, 312, 1010, 3256, 10836, 36094, 122544, 417150, 1437712, 4970904, 17333772, 60638124, 213435264, 753520804, 2672606464, 9505230397, 33928264990, 121400935184, 435660446342, 1566809204928, 5648450745204, 20402191885146, 73842311224632

Offset: 3

Author

N. J. A. Sloane

Keywords

• nonn

References

• C. F. Earl and L. J. March, Architectural applications of graph theory, pp. 327-355 of R. J. Wilson and L. W. Beineke, editors, Applications of Graph Theory. Academic Press, NY, 1979.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Andrew Howroyd, Table of n, a(n) for n = 3..500
• C. F. Earl and L. J. March, Architectural applications of graph theory, pp. 327-355 of R. J. Wilson and L. W. Beineke, editors, Applications of Graph Theory. Academic Press, NY, 1979. (Annotated scanned copy)

Crossrefs

Antidiagonal sums of the array in A169809.

Cf. A005027.

Extensions

Terms a(11) and beyond from Andrew Howroyd, Feb 22 2021