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4*9^n-1.
1

%I #15 Sep 08 2022 08:46:00

%S 3,35,323,2915,26243,236195,2125763,19131875,172186883,1549681955,

%T 13947137603,125524238435,1129718145923,10167463313315,91507169819843,

%U 823564528378595,7412080755407363,66708726798666275,600378541187996483

%N 4*9^n-1.

%H Vincenzo Librandi, <a href="/A198961/b198961.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 (10,-9).

%F a(n) = 9*a(n-1)+8. a(n) = 10*a(n-1)-9*a(n-2), n>1.

%F G.f.: (3 + 5*x)/(1 - 10*x + 9*x^2). - _Vincenzo Librandi_, Jan 03 2013

%t CoefficientList[Series[(3 + 5 x)/(1 - 10 x + 9 x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 03 2013 *)

%o (Magma) [4*9^n-1: n in [0..20]];

%K nonn,easy

%O 0,1

%A _Vincenzo Librandi_, Nov 01 2011