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 A133384 #38 Dec 01 2023 03:27:45
%S A133384 12,102,1002,10002,100002,1000002,10000002,100000002,1000000002,
%T A133384 10000000002,100000000002,1000000000002,10000000000002,
%U A133384 100000000000002,1000000000000002,10000000000000002,100000000000000002,1000000000000000002,10000000000000000002
%N A133384 Numbers with n 0's between 1 and 2.
%H A133384 Vincenzo Librandi, <a href="/A133384/b133384.txt">Table of n, a(n) for n = 0..200</a>
%H A133384 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A133384 a(n) = 10^(n+1) + 2. - _Vincenzo Librandi_, Aug 10 2011
%F A133384 a(n) = 11*a(n-1) - 10*a(n-2); a(0)=12, a(1)=102. - _Harvey P. Dale_, Oct 03 2013
%F A133384 From _Stefano Spezia_, Nov 30 2023: (Start)
%F A133384 O.g.f.: 6*(2 - 5*x)/((1 - x)*(1 - 10*x)).
%F A133384 E.g.f.: 2*exp(x)*(1 + 5*exp(9*x)).
%F A133384 (R(a(n)) + 1)/(a(n) - 1) = 2, where R(k) = A004086(k). (End)
%F A133384 a(n) = 6 * A126109(n). - _Alois P. Heinz_, Nov 30 2023
%t A133384 Table[FromDigits[Join[PadRight[{1},n,0],{2}]],{n,20}] (* or *) 10^Range[20]+2 (* or *) LinearRecurrence[{11,-10},{12,102},20] (* _Harvey P. Dale_, Oct 03 2013 *)
%o A133384 (Magma) [10^(n+1)+2: n in [0..20]]; // _Vincenzo Librandi_, Aug 10 2011
%Y A133384 Subsequence of A052148.
%Y A133384 Cf. A004086, A126109.
%K A133384 nonn,base,easy
%O A133384 0,1
%A A133384 _Paul Curtz_, Oct 29 2007