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 A198763 #17 Mar 15 2023 14:16:37
%S A198763 3,19,99,499,2499,12499,62499,312499,1562499,7812499,39062499,
%T A198763 195312499,976562499,4882812499,24414062499,122070312499,610351562499,
%U A198763 3051757812499,15258789062499,76293945312499,381469726562499,1907348632812499
%N A198763 a(n) = 4*5^n-1.
%H A198763 Vincenzo Librandi, <a href="/A198763/b198763.txt">Table of n, a(n) for n = 0..1000</a>
%H A198763 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (6,-5).
%F A198763 a(n) = 5*a(n-1)+4.
%F A198763 a(n) = 6*a(n-1)-5*a(n-2), n>1.
%F A198763 G.f.: (3 + x)/(1 - 6*x + 5*x^2). - _Vincenzo Librandi_, Jan 04 2013
%t A198763 CoefficientList[Series[(3 + x)/(1 - 6*x + 5*x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 04 2013 *)
%t A198763 NestList[5#+4&,3,30] (* or *) LinearRecurrence[{6,-5},{3,19},30] (* _Harvey P. Dale_, Jul 03 2021 *)
%o A198763 (Magma) [4*5^n-1: n in [0..30]]
%Y A198763 Cf. A024049, A057651, A081655.
%K A198763 nonn,easy
%O A198763 0,1
%A A198763 _Vincenzo Librandi_, Oct 30 2011