This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A199686 #17 Jun 10 2025 16:33:06
%S A199686 7,61,601,6001,60001,600001,6000001,60000001,600000001,6000000001,
%T A199686 60000000001,600000000001,6000000000001,60000000000001,
%U A199686 600000000000001,6000000000000001,60000000000000001,600000000000000001,6000000000000000001,60000000000000000001,600000000000000000001
%N A199686 a(n) = 6*10^n + 1.
%H A199686 Vincenzo Librandi, <a href="/A199686/b199686.txt">Table of n, a(n) for n = 0..1000</a>
%H A199686 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A199686 a(n) = 10*a(n-1) - 9.
%F A199686 a(n) = 11*a(n-1) - 10*a(n-2).
%F A199686 G.f.: (7-16*x)/((1-x)*(1-10*x)).
%F A199686 E.g.f.: exp(x)*(1 + 6*exp(9*x)). - _Elmo R. Oliveira_, Jun 10 2025
%t A199686 6*10^Range[0,20]+1 (* or *) LinearRecurrence[{11,-10},{7,61},20] (* _Harvey P. Dale_, Oct 23 2024 *)
%o A199686 (Magma) [6*10^n+1: n in [0..30]];
%K A199686 nonn,easy
%O A199686 0,1
%A A199686 _Vincenzo Librandi_, Nov 09 2011