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

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