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A026851 a(n) = T(2n,n+2), T given by A026736. 1
1, 6, 28, 121, 508, 2109, 8723, 36065, 149277, 618961, 2571503, 10704390, 44641793, 186492242, 780275596, 3269135406, 13713525610, 57588530626, 242068874444, 1018378855512, 4287501276956, 18062827159136, 76141329903018 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 2..1000

FORMULA

G.f.: (x * C(x)^5)/(1 - x/sqrt(1 - 4 * x)) where C(x) is the g.f. for Catalan numbers A000108. - David Callan, Jan 16 2016

a(n) ~ (3 - sqrt(5))^5 * (2 + sqrt(5))^(n+2) / (32*sqrt(5)). - Vaclav Kotesovec, Jul 18 2019

MATHEMATICA

CoefficientList[Series[(1-Sqrt[1-4x])^5/(32 x^5 (1-x/Sqrt[1-4x])), {x, 0, 30}], x] (* David Callan, Jan 16 2016 *)

PROG

(PARI) my(x='x+O('x^30)); Vec(sqrt(1-4*x)*(1-sqrt(1-4*x))^5/(32*x^3*(sqrt(1-4*x) -x)) ) \\ G. C. Greubel, Jul 17 2019

(MAGMA) R<x>:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( Sqrt(1-4*x)*(1-Sqrt(1-4*x))^5/(32*x^3*(Sqrt(1-4*x) -x)) )); // G. C. Greubel, Jul 17 2019

(Sage) a=(sqrt(1-4*x)*(1-sqrt(1-4*x))^5/(32*x^3*(sqrt(1-4*x)-x))).series(x, 30).coefficients(x, sparse=False); a[2:] # G. C. Greubel, Jul 17 2019

CROSSREFS

Cf. A000108, A026736.

Sequence in context: A037131 A292485 A225417 * A267689 A300996 A181337

Adjacent sequences:  A026848 A026849 A026850 * A026852 A026853 A026854

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified October 22 07:29 EDT 2019. Contains 328315 sequences. (Running on oeis4.)