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%I #22 Dec 23 2023 09:44:06
%S 1,2,9,33,126,477,1809,6858,26001,98577,373734,1416933,5372001,
%T 20366802,77216409,292749633,1109898126,4207943277,15953524209,
%U 60484402458,229313780001,869394547377,3296124982134
%N a(n) = 3*a(n-1)+3*a(n-2) with a(0)=1 and a(1)=2.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,3).
%F G.f.: (1-x)/(1-3*x-3*x^2).
%t LinearRecurrence[{3,3},{1,2},30] (* _Harvey P. Dale_, Aug 03 2020 *)
%o (PARI) Vec((1-x)/(1-3*x-3*x^2)+O(x^99)) \\ _Charles R Greathouse IV_, Jan 31 2012
%Y Cf. A104934, A112117.
%K nonn,easy
%O 0,2
%A _Philippe Deléham_, Dec 14 2011