A006434 Number of tree-rooted toroidal maps with 2 faces and n vertices and without separating loops or isthmuses. (Formerly M3708)

4, 120, 1230, 7424, 32424, 113584, 338742, 893220, 2136618, 4721728, 9770904

Offset

1,1

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=1..11.

T. R. S. Walsh and A. B. Lehman, Counting rooted maps by genus. III: Nonseparable maps, J. Combinatorial Theory Ser. B 18 (1975), 222-259.

Formula

Empirical g.f.: 2*x*(x^6+8*x^5-13*x^4+22*x^3+105*x^2+40*x+2) / (x-1)^10. - Colin Barker, Apr 09 2013

Crossrefs

Cf. A006435, A006436, A006439.

Sequence in context: A271421 A064204 A054644 * A240397 A347425 A002702

Adjacent sequences: A006431 A006432 A006433 * A006435 A006436 A006437

Keyword

nonn,more

Author

N. J. A. Sloane

Extensions

Name clarified by Andrew Howroyd, Apr 04 2021

Status

approved