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%I #17 Sep 08 2022 08:44:44
%S 4,12,37,115,358,1115,3473,10818,33697,104963,326950,1018419,3172281,
%T 9881362,30779529,95875387,298642966,930245227,2897627873,9025842914,
%U 28114666161,87574585651,272786737286,849705465187,2646753961545,8244393875250
%N a(n) = 3*a(n-1) + a(n-2) - 2*a(n-3) (agrees with A019480 for n <= 19 only).
%D R. K. Guy, personal communication.
%H Vincenzo Librandi, <a href="/A019481/b019481.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,1,-2)
%F From _R. J. Mathar_, Aug 22 2008: (Start)
%F O.g.f.: (4 - 3*x^2)/(1 - 3*x - x^2 + 2*x^3).
%F a(n) = 4*A100058(n) - 3*A100058(n-2). (End)
%t LinearRecurrence[{3,1, -2}, {4, 12, 37}, 30] (* _Harvey P. Dale_, Jan 17 2017 *)
%o (Magma) I:=[4, 12, 37]; [n le 3 select I[n] else 3*Self(n-1)+Self(n-2)-2*Self(n-3): n in [1..30]]; // _Vincenzo Librandi_, Jan 18 2017
%K nonn,easy
%O 0,1
%A _N. J. A. Sloane_
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