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A006428 Number of tree-rooted planar maps with 3 vertices and n faces.
(Formerly M3139)
0
0, 3, 36, 135, 360, 798, 1568, 2826, 4770, 7645, 11748, 17433 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

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

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

LINKS

Table of n, a(n) for n=1..12.

FORMULA

a(n) seems to be divisible by n+1. - Ralf Stephan, Sep 01 2003

Conjecture (for n > 1): a(n) = n*(n+1)*(n^3+6*n^2+11*n-42) / 24. - Sean A. Irvine, Apr 10 2017

CROSSREFS

Sequence in context: A268591 A275560 A213848 * A068619 A247768 A168075

Adjacent sequences:  A006425 A006426 A006427 * A006429 A006430 A006431

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Title improved by Sean A. Irvine, Apr 10 2017

STATUS

approved

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Last modified November 21 09:14 EST 2019. Contains 329362 sequences. (Running on oeis4.)