%I #16 Sep 08 2022 08:46:00
%S 7,79,799,7999,79999,799999,7999999,79999999,799999999,7999999999,
%T 79999999999,799999999999,7999999999999,79999999999999,
%U 799999999999999,7999999999999999,79999999999999999,799999999999999999,7999999999999999999
%N 8*10^n-1.
%H Vincenzo Librandi, <a href="/A198973/b198973.txt">Table of n, a(n) for n = 0..200</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F a(n) = 10*a(n-1)+9.
%F a(n) = 11*a(n-1)-10*a(n-2), n>1.
%F G.f.: (7 + 2*x)/(1 - 11*x + 10*x^2). - _Vincenzo Librandi_, Jan 04 2013
%t Table[FromDigits[PadRight[{7},n,9]],{n,20}] (* _Harvey P. Dale_, Jun 05 2012 *)
%t CoefficientList[Series[(7 + 2*x)/(1 - 11*x + 10*x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 04 2013 *)
%o (Magma) [8*10^n-1 : n in [0..20]]
%K nonn,easy
%O 0,1
%A _Vincenzo Librandi_, Nov 02 2011
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