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%I #13 May 09 2024 04:33:50
%S 1,-3,21,-27,189,-243,1701,-2187,15309,-19683,137781,-177147,1240029,
%T -1594323,11160261,-14348907,100442349,-129140163,903981141,
%U -1162261467,8135830269,-10460353203,73222472421,-94143178827,659002251789,-847288609443
%N Expansion of (1-3*x+12*x^2)/((1-3*x)*(1+3*x)).
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,9).
%F a(n) = 2*3^n/3 + 5*(-3)^n/3 - 4*0^n/3.
%F a(0)=1, a(2n-1)=-k^(2n-1), a(2n)=(3k-2)*k^(2n-1), where k=3.
%F G.f.: (1-k*x+2*(k-1)*k*x^2)/((1-k*x)*(1+k*x)), where k=3.
%K easy,sign
%O 0,2
%A _Paul Barry_, Dec 22 2003