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%I #11 Feb 06 2024 11:57:44
%S 1,2,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,
%T 2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,
%U 2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4
%N Expansion of (1 + x^2)*(1 + 2*x)/(1 - x^2).
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).
%F a(0)=1, a(n)=(2-0^((n-1)/2))(1-(-1)^n)+(2-0^(n/2))(1+(-1)^n)/2, n>1.
%t CoefficientList[Series[(1+x^2)(1+2x)/(1-x^2),{x,0,95}],x] (* _James C. McMahon_, Feb 02 2024 *)
%Y Row sums of A106468.
%K easy,nonn
%O 0,2
%A _Paul Barry_, May 03 2005
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