OFFSET
2,2
COMMENTS
Also a(n) = T(2n,n-2) = T(2n+1,n+2), T given by A026725.
Also a(n) = T(2n,n-2), T given by A026736.
Column k=6 of triangle A236830. - Philippe Deléham, Feb 02 2014
LINKS
G. C. Greubel, Table of n, a(n) for n = 2..1000
FORMULA
G.f.: (x^2*C(x)^6)/(1-x*C(x)^3) where C(x) is the g.f. of A000108. - Philippe Deléham, Feb 02 2014
-(n+2)*(3*n-7)*a(n) +2*(12*n^2-19*n-16)*a(n-1) +5*(-9*n^2+27*n-22)*a(n-2) -2*(3*n-4)*(2*n-3)*a(n-3)=0. - R. J. Mathar, Oct 26 2019
MATHEMATICA
Drop[CoefficientList[Series[(1-Sqrt[1-4*x])^6/(8*x^2*(8*x^2-(1-Sqrt[1 - 4*x])^3)), {x, 0, 30}], x], 2] (* G. C. Greubel, Jul 16 2019 *)
PROG
(PARI) my(x='x+O('x^30)); Vec( (1-sqrt(1-4*x))^6/(8*x^2*(8*x^2 -(1-sqrt(1-4*x))^3))) \\ G. C. Greubel, Jul 16 2019
(Magma) R<x>:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( (1-Sqrt(1-4*x))^6/(8*x^2*(8*x^2 -(1-Sqrt(1-4*x))^3)) )); // G. C. Greubel, Jul 16 2019
(Sage) a=((1-sqrt(1-4*x))^6/(8*x^2*(8*x^2 -(1-sqrt(1-4*x))^3))).series(x, 30).coefficients(x, sparse=False); a[2:] # G. C. Greubel, Jul 16 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved