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%I #16 Dec 04 2019 19:10:28
%S 1,2,9,18,81,162,729,1458,6561,13122,59049,118098,531441,1062882,
%T 4782969,9565938,43046721,86093442,387420489,774840978,3486784401,
%U 6973568802,31381059609,62762119218,282429536481,564859072962
%N a(n) = (5*3^n + (-3)^n)/6.
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (0,9)
%F From _Reinhard Zumkeller_, Mar 04 2011: (Start)
%F G.f.: (1+2x)/((1-3x)*(1+3x)).
%F E.g.f.: (5*exp(3x) + exp(-3x))/6.
%F a(n+3) = a(n+2)*a(n+1)/a(n). (End)
%F a(n) = 9*a(n-2). - _Vincenzo Librandi_, Mar 20 2011
%t LinearRecurrence[{0,9},{1,2},30] (* _Harvey P. Dale_, Dec 04 2019 *)
%Y Cf. A083424.
%K easy,nonn
%O 0,2
%A _Paul Barry_, Apr 30 2003
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