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%I #17 Mar 20 2022 22:55:29
%S 1,4,9,36,81,324,729,2916,6561,26244,59049,236196,531441,2125764,
%T 4782969,19131876,43046721,172186884,387420489,1549681956,3486784401,
%U 13947137604,31381059609,125524238436,282429536481,1129718145924,2541865828329,10167463313316
%N A133080 * A000244.
%C A133647 is a companion sequence.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0, 9).
%F A133080 * A000244, where A000244 = (3^0, 3^1, 3^2, ...). For even n, a(n) = 3^n. For odd n, a(n) = 4 * 3^(n-1).
%F G.f.: (1+4x)/((1+3x)(1-3x)). a(n) = 9*a(n-2). - _R. J. Mathar_, Oct 30 2008
%F a(n) = A038754(n)^2. - _T. D. Noe_, Jun 10 2011
%e a(4) = 3^4 = 81.
%e a(5) = 324 = 4 * 3^4.
%t Table[3^(n - 2) ((-1)^n + 7)/2, {n, 1, 60}] (* _Vladimir Joseph Stephan Orlovsky_, Jun 10 2011 *)
%t LinearRecurrence[{0,9},{1,4},30] (* _Harvey P. Dale_, Mar 27 2017 *)
%Y Cf. A000244, A133647.
%K nonn
%O 0,2
%A _Gary W. Adamson_, Sep 19 2007
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