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 A199750 #14 Sep 08 2022 08:46:00
%S A199750 3,23,243,2663,29283,322103,3543123,38974343,428717763,4715895383,
%T A199750 51874849203,570623341223,6276856753443,69045424287863,
%U A199750 759499667166483,8354496338831303,91899459727144323,1010894056998587543,11119834626984462963
%N A199750 2*11^n+1.
%H A199750 Vincenzo Librandi, <a href="/A199750/b199750.txt">Table of n, a(n) for n = 0..900</a>
%H A199750 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (12,-11).
%F A199750 a(n) = 11*a(n-1)-10.
%F A199750 a(n) = 12*a(n-1)-11*a(n-2).
%F A199750 G.f.: (3-13*x)/((1-x)*(1-11*x)).
%t A199750 2*11^Range[0,20]+1 (* or *) LinearRecurrence[{12,-11},{3,23},20] (* _Harvey P. Dale_, Aug 14 2012 *)
%o A199750 (Magma) [2*11^n+1: n in [0..30]];
%K A199750 nonn,easy
%O A199750 0,1
%A A199750 _Vincenzo Librandi_, Nov 10 2011