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 A199028 #20 Apr 02 2025 20:29:12
%S A199028 4,49,544,5989,65884,724729,7972024,87692269,964614964,10610764609,
%T A199028 116718410704,1283902517749,14122927695244,155352204647689,
%U A199028 1708874251124584,18797616762370429,206773784386074724,2274511628246821969,25019627910715041664,275215907017865458309
%N A199028 a(n) = (9*11^n - 1)/2.
%H A199028 Vincenzo Librandi, <a href="/A199028/b199028.txt">Table of n, a(n) for n = 0..900</a>
%H A199028 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (12,-11).
%F A199028 a(n) = 11*a(n-1) + 5.
%F A199028 a(n) = 12*a(n-1) - 11*a(n-2).
%F A199028 G.f.: (4 + x)/(1 - 12*x + 11*x^2). - _Vincenzo Librandi_, Jan 04 2013
%F A199028 From _Elmo R. Oliveira_, Apr 02 2025: (Start)
%F A199028 E.g.f.: exp(x)*(9*exp(10*x) - 1)/2.
%F A199028 a(n) = A199029(n)/2. (End)
%t A199028 CoefficientList[Series[(4 + x)/(1 - 12 x + 11 x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 04 2013 *)
%o A199028 (Magma) [(9*11^n-1)/2: n in [0..20]];
%Y A199028 Cf. A199029.
%K A199028 nonn,easy
%O A199028 0,1
%A A199028 _Vincenzo Librandi_, Nov 02 2011