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%I #21 Mar 29 2020 07:04:51
%S 0,3,12,90,528,3372,20880,130728,815232,5091120,31777728,198386592,
%T 1238434560,7731150528,48262685952,301286851200,1880825008128,
%U 11741315949312,73296813911040,457565678934528,2856418110492672,17831591947054080,111316221335113728
%N a(n) = ((2 + 3*sqrt(2))^n - (2 - 3*sqrt(2))^n)/(2*sqrt(2)).
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,14).
%F From _Philippe Deléham_, Dec 12 2006: (Start)
%F a(n) = 4*a(n-1) + 14*a(n-2) for n >= 2; a(0)=0, a(1)=3.
%F G.f.: 3x/(1-4*x-14*x^2). (End)
%t Expand[Table[((2 + 3Sqrt[2])^n - (2 - 3Sqrt[2])^n)/(2Sqrt[2]), {n, 0, 30}]]
%t LinearRecurrence[{4, 14}, {0, 3}, 50] (* _Amiram Eldar_, Mar 29 2020 *)
%K nonn,easy
%O 1,2
%A _Artur Jasinski_, Dec 10 2006
%E More terms from _Amiram Eldar_, Mar 29 2020