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A019481 a(n) = 3*a(n-1) + a(n-2) - 2*a(n-3) (agrees with A019480 for n <= 19 only). 4

%I

%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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Last modified June 5 01:27 EDT 2020. Contains 334828 sequences. (Running on oeis4.)