A006403 Number of unsensed 2-connected planar maps with n edges. (Formerly M0808)

0, 1, 2, 3, 6, 15, 36, 114, 396, 1565, 6756, 31563, 154370, 785113, 4099948, 21870704, 118624544, 652485364, 3631820462, 20426666644, 115949791342, 663640383400, 3826858500878, 22218232389849, 129802836253994

Offset

1,3

Comments

The maps considered here may include parallel edges. - Andrew Howroyd, Jan 13 2025

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Timothy R. Walsh, personal communication.

Links

Table of n, a(n) for n=1..25.

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

Timothy R. Walsh, Number of sensed planar maps with n edges and m vertices, p. 41.

Formula

a(n) = (A006402(n) + A006444(n))/2. - Andrew Howroyd, Jan 13 2025

Crossrefs

Row sums of A379432.

Cf. A000139 (rooted), A006385, A006402 (sensed), A006407 (without parallel edges), A006444 (achiral).

Sequence in context: A053561 A237585 A147773 * A129960 A115098 A036418

Adjacent sequences: A006400 A006401 A006402 * A006404 A006405 A006406

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(23)-a(25) added by Andrew Howroyd, Jan 13 2025

Status

approved