A026675 a(n) = T(2n-1,n-2), T given by A026670. Also T(2n-1,n-2) = T(2n,n+2), T given by A026725 and T(2n,n-2), T given by A026736.

1, 6, 29, 131, 575, 2488, 10681, 45641, 194467, 827045, 3512983, 14909339, 63239487, 268127302, 1136495965, 4816202207, 20406887583, 86457399359, 366263778659, 1551535465465, 6572224024539, 27838835937511, 117918419518219

Offset: 2

Author

Clark Kimberling

Keywords

• nonn

Comments

Column k=5 of triangle A236830. - Philippe Deléham, Feb 02 2014

Links

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

Crossrefs

Cf. A000108, A026670, A026725, A026736, A236830.

Programs

Magma

R:=PowerSeriesRing(Rationals(), 30); Coefficients(R!(  (1-Sqrt(1-4*x))^5/(4*x*(8*x^2 -(1-Sqrt(1-4*x))^3)) )); // G. C. Greubel, Jul 16 2019

Mathematica

Drop[CoefficientList[Series[(1-Sqrt[1-4*x])^5/(4*x*(8*x^2 -(1-Sqrt[1 - 4*x])^3)), {x,0,30}], x], 2] (* G. C. Greubel, Jul 16 2019 *)

PARI

my(x='x+O('x^30)); Vec( (1-sqrt(1-4*x))^5/(4*x*(8*x^2 -(1-sqrt(1-4*x))^3))) \\ G. C. Greubel, Jul 16 2019

Sage

a=((1-sqrt(1-4*x))^5/(4*x*(8*x^2 -(1-sqrt(1-4*x))^3))).series(x, 30).coefficients(x, sparse=False); a[2:] # G. C. Greubel, Jul 16 2019

Formula

G.f.: (x^2*C(x)^5)/(1-x*C(x)^3) where C(x) is the g.f. of A000108. - Philippe Deléham, Feb 02 2014