A006406 - OEIS

A006406

Number of 2-connected planar maps with n edges (see reference for precise definition).
(Formerly M1195)

1, 1, 2, 4, 9, 24, 81, 274, 1071, 4357, 18416, 80040, 356109, 1610910, 7399114

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OFFSET

3,3

COMMENTS

Equivalently, a(n) is the number of embeddings on the sphere of 2-connected planar graphs with n edges up to orientation preserving isomorphisms. - Andrew Howroyd, Mar 27 2021

REFERENCES

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=3..17.

Timothy R. Walsh, Generating nonisomorphic maps without storing them, SIAM J. Algebraic Discrete Methods 4 (1983), no. 2, 161-178.

FORMULA

a(n) = Sum_{k=3..n} A342059(k, n+2-k). - Andrew Howroyd, Mar 27 2021

CROSSREFS

Cf. A006402, A006404, A006407 (unsensed case), A342059.

Sequence in context: A210342 A137154 A098448 * A097656 A324148 A012936

Adjacent sequences: A006403 A006404 A006405 * A006407 A006408 A006409

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane

EXTENSIONS

a(11) and a(12) from Sean A. Irvine, Apr 02 2017

a(13)-a(17) from Andrew Howroyd, Mar 27 2021

STATUS

approved