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Expansion of 1/(1 - 4*x + 2*x^2 + 4*x^3 - 2*x^4).
1

%I #15 Sep 08 2022 08:44:49

%S 1,4,14,44,134,400,1184,3488,10252,30096,88296,258960,759368,2226560,

%T 6528256,19140352,56117392,164528960,482376160,1414257856,4146398048,

%U 12156629760,35641443840,104495439360

%N Expansion of 1/(1 - 4*x + 2*x^2 + 4*x^3 - 2*x^4).

%H Vincenzo Librandi, <a href="/A027831/b027831.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (4,-2,-4,2)

%F a(n) = 4*a(n-1) - 2*a(n-2) - 4*a(n-3) + 2*a(n-4). - _Vincenzo Librandi_, Jun 20 2012

%t LinearRecurrence[{4,-2,-4,2},{1,4,14,44},40] (* _Vincenzo Librandi_, Jun 20 2012 *)

%o (Magma) I:=[1, 4, 14, 44]; [n le 4 select I[n] else 4*Self(n-1)-2*Self(n-2)-4*Self(n-3)+2*Self(n-4): n in [1..40]]; // _Vincenzo Librandi_, Jun 20 2012

%K nonn,easy

%O 0,2

%A _N. J. A. Sloane_