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a(n) = 2*3^n - 3*2^n.
3

%I #27 Feb 08 2024 09:46:59

%S -1,0,6,30,114,390,1266,3990,12354,37830,115026,348150,1050594,

%T 3164070,9516786,28599510,85896834,257887110,774054546,2322950070,

%U 6970423074,20914414950,62749536306,188261191830,564808741314,1694476555590,5083530330066,15250792316790

%N a(n) = 2*3^n - 3*2^n.

%C Essentially 2 * A210448. - _Joerg Arndt_, Aug 03 2014

%H Vincenzo Librandi, <a href="/A245804/b245804.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,-6).

%F G.f.: (-1 +5*x)/((1-2*x)(1-3*x)).

%F a(n) = 5*a(n-1) -6*a(n-2) for n>1.

%F a(n) = A008776(n) - A007283(n). - _Michel Marcus_, Aug 03 2014

%t CoefficientList[Series[(-1 + 5 x)/((1 - 2 x) (1 - 3 x)), {x, 0, 30}], x]

%t Table[(2 3^n - 3 2^n), {n, 0, 30}] (* _Vincenzo Librandi_, Aug 04 2014 *)

%o (Magma) [2*3^n-3*2^n: n in [0..40]]; /* or */ I:=[-1,0]; [n le 2 select I[n] else 5*Self(n-1)-6*Self(n-2): n in [1..30]];

%Y Cf. A007283, A008776.

%K sign,easy

%O 0,3

%A _Vincenzo Librandi_, Aug 03 2014