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%I #17 May 10 2024 10:58:48
%S 1,2,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,
%T -1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,0,-1,1,
%U 0,-1,1,0,-1,1,0,-1,1,0
%N Expansion of (1+x)^3/(1+x+x^2).
%C Row sums of number triangle A122433. Binomial transform is A077859.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1).
%F a(n) = 2*sqrt(3)*cos(2*Pi*n/3+Pi/6)/3+C(1,n)+C(0,n).
%F a(n) = -A049347(n) if n>=2 . - _R. J. Mathar_, Feb 08 2008
%t CoefficientList[Series[(1+x)^3/(1+x+x^2),{x,0,70}],x] (* or *) PadRight[ {1,2,0},71,{-1,1,0}] (* _Harvey P. Dale_, Apr 25 2012 *)
%K easy,sign
%O 0,2
%A _Paul Barry_, Sep 04 2006