A005027 Number of trivalent maps with n nodes.

1, 2, 4, 16, 63, 328, 1933, 12633, 87466, 633015, 4717745, 35980100, 279418926, 2202903618, 17590599410, 142025760202, 1157868883224, 9520828261067, 78888071847324, 658158709983945, 5525145717439001, 46644670326913204, 395812792437224022, 3374572617006946447

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 array in A169808.

Programs

PARI

\\ See link in A169808 for script.
A169808AntidiagonalSums(25) \\ Andrew Howroyd, Feb 22 2021

Formula

a(n) = (A005028(n) + A341855(n))/2. - Andrew Howroyd, Feb 22 2021

Extensions

a(10) corrected and terms a(11) and beyond from Andrew Howroyd, Feb 22 2021