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A026759
a(n) = T(2n, n), T given by A026758.
10
1, 2, 7, 27, 109, 453, 1922, 8284, 36155, 159435, 709246, 3178992, 14343567, 65099245, 297015765, 1361584755, 6268757195, 28975155915, 134410918700, 625578384150, 2920488902795, 13672762887465, 64179220019365, 301987822527627
OFFSET
0,2
LINKS
FORMULA
a(n) = A002212(n+1) - A000245(n). - David Callan, Feb 01 2014
G.f.: ((1-x)*sqrt(1 - 4*x) - sqrt(1 - 6*x + 5*x^2))/(2*x^2). - G. C. Greubel, Oct 31 2019
MAPLE
seq(coeff(series(((1-x)*sqrt(1-4*x) - sqrt(1 -6*x +5*x^2))/(2*x^2), x, n+2), x, n), n = 0..30); # G. C. Greubel, Oct 31 2019
MATHEMATICA
CoefficientList[Normal[Series[((1-x)Sqrt[1-4x] -Sqrt[1-6x+5x^2])/(2x^2), {x, 0, 30}]], x] (* David Callan, Feb 01 2014 *)
PROG
(PARI) my(x='x+O('x^30)); Vec(((1-x)*sqrt(1 - 4*x) - sqrt(1 - 6*x + 5*x^2))/(2*x^2)) \\ G. C. Greubel, Oct 31 2019
(Magma) R<x>:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( ((1-x)*Sqrt(1 - 4*x) - Sqrt(1 - 6*x + 5*x^2))/(2*x^2) )); // G. C. Greubel, Oct 31 2019
(Sage)
def A077952_list(prec):
P.<x> = PowerSeriesRing(ZZ, prec)
return P(((1-x)*sqrt(1-4*x) - sqrt(1-6*x+5*x^2))/(2*x^2)).list()
A077952_list(30) # G. C. Greubel, Oct 31 2019
KEYWORD
nonn
STATUS
approved