A006407 Number of unsensed 2-connected simple planar maps with n edges.

1, 1, 2, 4, 8, 20, 58, 177, 630, 2410, 9772, 41423, 181586, 814412, 3722445

Offset: 3

Author

N. J. A. Sloane

Keywords

• nonn
• more

Comments

A simple planar map is a planar map without loops or parallel edges.

Equivalently, a(n) is the number of embeddings on the sphere of 2-connected planar graphs with n edges. - 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

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

Crossrefs

Cf. A006403, A006405, A006406 (sensed case), A342060, A379437 (rooted).

Formula

a(n) = Sum_{k=3..n} A342060(k, n+2-k). - Andrew Howroyd, Mar 27 2021

Extensions

a(11) and a(12) from Sean A. Irvine, Apr 03 2017

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