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A026853 a(n) = T(2n,n+4), T given by A026736. 1
1, 10, 66, 365, 1837, 8741, 40133, 179932, 793605, 3460106, 14961664, 64306917, 275180827, 1173714565, 4994096327, 21211537533, 89972566673, 381261067469, 1614446775255, 6832832045575, 28908094009481, 122272843951891, 517095189163181 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 4..1000

FORMULA

G.f.: x^4*C(x)^9/(1 -x/sqrt(1-4*x)), where C(x) if the g.f. for Catalan numbers A000108. - G. C. Greubel, Jul 17 2019

a(n) ~ (3 - sqrt(5))^9 * (2 + sqrt(5))^(n+4) / (512*sqrt(5)). - Vaclav Kotesovec, Jul 18 2019

MATHEMATICA

Drop[CoefficientList[Series[Sqrt[1-4x]*(1-Sqrt[1-4x])^9/(512*x^5*(Sqrt[1-4x]-x)), {x, 0, 40}], x], 4] (* G. C. Greubel, Jul 17 2019 *)

PROG

(PARI) my(x='x+O('x^40)); Vec(sqrt(1-4*x)*(1-sqrt(1-4*x))^9/(512*x^5*(sqrt(1-4*x) -x)) ) \\ G. C. Greubel, Jul 17 2019

(MAGMA) R<x>:=PowerSeriesRing(Rationals(), 40); Coefficients(R!( Sqrt(1-4*x)*(1-Sqrt(1-4*x))^9/(512*x^5*(Sqrt(1-4*x) -x)) )); // G. C. Greubel, Jul 17 2019

(Sage) a=(sqrt(1-4*x)*(1-sqrt(1-4*x))^9/(512*x^5*(sqrt(1-4*x)-x))).series(x, 40).coefficients(x, sparse=False); a[4:] # G. C. Greubel, Jul 17 2019

CROSSREFS

Cf. A000108, A026736.

Sequence in context: A080421 A320817 A004310 * A177452 A033504 A163615

Adjacent sequences:  A026850 A026851 A026852 * A026854 A026855 A026856

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified April 13 10:24 EDT 2021. Contains 342935 sequences. (Running on oeis4.)