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 A199020 #21 Apr 10 2025 21:18:10
%S A199020 3,43,483,5323,58563,644203,7086243,77948683,857435523,9431790763,
%T A199020 103749698403,1141246682443,12553713506883,138090848575723,
%U A199020 1518999334332963,16708992677662603,183798919454288643,2021788113997175083
%N A199020 a(n) = 4*11^n-1.
%H A199020 Vincenzo Librandi, <a href="/A199020/b199020.txt">Table of n, a(n) for n = 0..900</a>
%H A199020 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (12,-11).
%F A199020 a(n) = 11*a(n-1)+10.
%F A199020 a(n) = 12*a(n-1)-11*a(n-2), n>1.
%F A199020 G.f.: (3 + 7*x)/(1 - 12*x + 11*x^2). - _Vincenzo Librandi_, Jan 04 2013
%t A199020 4*11^Range[0,20]-1 (* or *) LinearRecurrence[{12,-11},{3,43},20] (* _Harvey P. Dale_, Aug 25 2012 *)
%t A199020 CoefficientList[Series[(3 + 7*x)/(1 - 12*x + 11*x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 04 2013 *)
%o A199020 (Magma) [4*11^n-1 : n in [0..20]];
%K A199020 nonn,easy
%O A199020 0,1
%A A199020 _Vincenzo Librandi_, Nov 02 2011