A006415 - OEIS

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A006415

Number of nonseparable toroidal tree-rooted maps with n + 3 edges and n + 1 vertices.
(Formerly M3705)

4, 104, 1020, 6092, 26670, 94128, 283338, 754380, 1821534, 4061200

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,1

COMMENTS

The number of faces is 2. - Andrew Howroyd, Apr 05 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=0..9.

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

Conjecture: a(n) = 4 * binomial(n + 4, n) + 84 * binomial(n + 4, n - 1) + 456 * binomial(n + 4, n - 2) + 996 * binomial(n + 4, n - 3) + 950 * binomial(n + 4, n - 4) + 330 * binomial(n + 5, n - 5). - Sean A. Irvine, Apr 03 2017

CROSSREFS

Cf. A006414, A006441.

Sequence in context: A331456 A211150 A281534 * A333434 A181396 A354063

Adjacent sequences: A006412 A006413 A006414 * A006416 A006417 A006418

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane

STATUS

approved