OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: 1-4*x/sqrt(1-8*x).
a(0)=1, a(n) = -2^(n+1)*(2*(n-1))!/(n-1)!^2.
D-finite with recurrence: (n-1)*a(n) +4*(3-2*n)*a(n-1)=0. - R. J. Mathar, Sep 26 2012
MATHEMATICA
CoefficientList[Series[(Sqrt[1-8x]-4x)/Sqrt[1-8x], {x, 0, 20}], x] (* Harvey P. Dale, May 06 2017 *)
PROG
(PARI) x='x+O('x^30); Vec((sqrt(1-8*x)-4*x)/sqrt(1-8*x)) \\ G. C. Greubel, Feb 03 2018
(Magma) Q:=Rationals(); R<x>:=PowerSeriesRing(Q, 40); Coefficients(R!((sqrt(1-8*x)-4*x)/sqrt(1-8*x))) // G. C. Greubel, Feb 03 2018
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Sep 16 2004
STATUS
approved