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A052756 E.g.f.: (-1/3)*LambertW(-3*x). 4
0, 1, 6, 81, 1728, 50625, 1889568, 85766121, 4586471424, 282429536481, 19683000000000, 1531578985264449, 131621703842267136, 12381557655576425121, 1265437718438866624512, 139628860198736572265625, 16543163447903718821855232, 2094704750199298376445300801 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Previous name was: A simple grammar.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..330

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 712

FORMULA

E.g.f.: (-1/3)*LambertW(-3*x).

For n>0, a(n) = (3*n)^(n-1). - Vaclav Kotesovec, Sep 30 2013

a(n) = [x^n] x/(1 - 3*n*x). - Ilya Gutkovskiy, Oct 12 2017

MAPLE

spec := [S, {S=Prod(B, B, B, Z), B=Set(S)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

MATHEMATICA

With[{nn=20}, CoefficientList[Series[-1/3 LambertW[-3x], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jun 01 2013 *)

PROG

(PARI) x='x+O('x^50); concat([0], Vec(serlaplace((-1/3)*lambertw(-3*x)))) \\ G. C. Greubel, Nov 05 2017

CROSSREFS

Sequence in context: A197076 A234872 A064341 * A193265 A138457 A252821

Adjacent sequences:  A052753 A052754 A052755 * A052757 A052758 A052759

KEYWORD

easy,nonn

AUTHOR

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

EXTENSIONS

New name using e.g.f. by Vaclav Kotesovec, Sep 30 2013

STATUS

approved

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Last modified February 24 15:37 EST 2018. Contains 299623 sequences. (Running on oeis4.)