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10^n+2*n.
1

%I #12 Sep 08 2022 08:45:50

%S 1,12,104,1006,10008,100010,1000012,10000014,100000016,1000000018,

%T 10000000020,100000000022,1000000000024,10000000000026,

%U 100000000000028,1000000000000030,10000000000000032,100000000000000034

%N 10^n+2*n.

%H Vincenzo Librandi, <a href="/A173835/b173835.txt">Table of n, a(n) for n = 0..100</a>

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (12,-21,10).

%F G.f.: (1-19*x^2)/((1-x)^2*(1-10*x)). - _Vincenzo Librandi_, Jul 06 2012

%F a(n) = 11*a(n-1) -10*a(n-2) -18. - _Vincenzo Librandi_, Jul 06 2012

%t CoefficientList[Series[(1-19*x^2)/((1-x)^2*(1-10*x)),{x,0,40}],x] (* _Vincenzo Librandi_, Jul 06 2012 *)

%t LinearRecurrence[{12,-21,10},{1,12,104},20] (* _Harvey P. Dale_, Dec 01 2015 *)

%o (Magma) I:=[1, 12]; [n le 2 select I[n] else 11*Self(n-1)-10*Self(n-2)-18: n in [1..20]]; // _Vincenzo Librandi_, Jul 06 2012

%K nonn,easy

%O 0,2

%A _Vincenzo Librandi_, Feb 26 2010