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A126982 Expansion of 1/(1+3*x*c(x)), c(x) the g.f. of Catalan numbers A000108. 7
1, -3, 6, -15, 30, -78, 144, -423, 630, -2490, 1956, -16998, -5844, -142860, -235740, -1475415, -3951450, -17627490, -57571740, -228692610, -810889020, -3098590020, -11377872720, -43011709110, -160518364740, -606261789828 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Hankel transform is (-3)^n.

Catalan transform of the sequence (-1)^n*A000244(n). - R. J. Mathar, Nov 11 2008

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

FORMULA

a(n) = Sum_{k=0..n} A039599(n,k)*(-4)^k.

G.f.: 2/(5 - 3*sqrt(1-4*x)). - G. C. Greubel, May 28 2019

MATHEMATICA

CoefficientList[Series[2/(5-3*Sqrt[1-4*x]), {x, 0, 30}], x] (* G. C. Greubel, May 28 2019 *)

PROG

(PARI) my(x='x+O('x^30)); Vec(2/(5-3*sqrt(1-4*x))) \\ G. C. Greubel, May 28 2019

(MAGMA) R<x>:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( 2/(5-3*Sqrt(1-4*x)) )); // G. C. Greubel, May 28 2019

(Sage) (2/(5-3*sqrt(1-4*x))).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, May 28 2019

CROSSREFS

Cf. A000108, A000244, A039599.

Sequence in context: A183038 A141023 A242172 * A256281 A034739 A276670

Adjacent sequences:  A126979 A126980 A126981 * A126983 A126984 A126985

KEYWORD

sign

AUTHOR

Philippe Deléham, Mar 21 2007

EXTENSIONS

Extended by R. J. Mathar, Nov 11 2008

STATUS

approved

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Last modified October 15 00:14 EDT 2019. Contains 328025 sequences. (Running on oeis4.)