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7*(10^n-9).
1

%I #18 Nov 30 2022 15:21:43

%S 7,637,6937,69937,699937,6999937,69999937,699999937,6999999937,

%T 69999999937,699999999937,6999999999937,69999999999937,

%U 699999999999937,6999999999999937,69999999999999937,699999999999999937

%N 7*(10^n-9).

%H Vincenzo Librandi, <a href="/A175601/b175601.txt">Table of n, a(n) for n = 1..100</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).

%F G.f.: 7*x*(1 + 80*x)/((1 - x)*(1 - 10*x)). - _Vincenzo Librandi_, Aug 23 2014

%F a(n) = 11*a(n-1) - 10*a(n-2). - _Vincenzo Librandi_, Aug 23 2014

%t CoefficientList[Series[7 (1 + 80 x)/((1 - x) (1 - 10 x)), {x, 0, 20}], x] (* _Vincenzo Librandi_, Aug 23 2014 *)

%t LinearRecurrence[{11,-10},{7,637},20] (* _Harvey P. Dale_, Nov 30 2022 *)

%o (Magma) [7*(10^n-9): n in [1..20]]; // _Vincenzo Librandi_, Aug 23 2014

%K nonn

%O 1,1

%A _Vincenzo Librandi_