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 A199764 #13 Sep 08 2022 08:46:00
%S A199764 11,111,1211,13311,146411,1610511,17715611,194871711,2143588811,
%T A199764 23579476911,259374246011,2853116706111,31384283767211,
%U A199764 345227121439311,3797498335832411,41772481694156511,459497298635721611,5054470284992937711
%N A199764 10*11^n+1.
%H A199764 Vincenzo Librandi, <a href="/A199764/b199764.txt">Table of n, a(n) for n = 0..900</a>
%H A199764 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (12,-11).
%F A199764 a(n) = 11*a(n-1)-10.
%F A199764 a(n) = 12*a(n-1)-11*a(n-2).
%F A199764 G.f.: (11-21*x)/((1-x)*(1-11*x)).
%t A199764 NestList[11#-10&,11,20] (* or *) LinearRecurrence[{12,-11},{11,111},20] (* _Harvey P. Dale_, Aug 28 2021 *)
%o A199764 (Magma) [10*11^n+1: n in [0..20]];
%K A199764 nonn,easy
%O A199764 0,1
%A A199764 _Vincenzo Librandi_, Nov 10 2011