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 A199209 #16 Mar 02 2023 12:40:41
%S A199209 11,41,161,641,2561,10241,40961,163841,655361,2621441,10485761,
%T A199209 41943041,167772161,671088641,2684354561,10737418241,42949672961,
%U A199209 171798691841,687194767361,2748779069441,10995116277761,43980465111041
%N A199209 a(n) = 10*4^n+1.
%C A199209 Bisection (odd part) of A083575. - _Bruno Berselli_, Nov 04 2011
%H A199209 Vincenzo Librandi, <a href="/A199209/b199209.txt">Table of n, a(n) for n = 0..1000</a>
%H A199209 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,-4).
%F A199209 a(n) = 4*a(n-1)-3.
%F A199209 a(n) = 5*a(n-1)-4*a(n-2).
%F A199209 G.f.: (11-14*x)/((1-x)*(1-4*x)). - _Bruno Berselli_, Nov 04 2011
%t A199209 10*4^Range[0,30]+1 (* or *) LinearRecurrence[{5,-4},{11,41},30] (* _Harvey P. Dale_, May 27 2019 *)
%o A199209 (Magma) [10*4^n+1: n in [0..30]];
%Y A199209 Cf. A083575.
%K A199209 nonn,easy
%O A199209 0,1
%A A199209 _Vincenzo Librandi_, Nov 04 2011