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 A199113 #18 Mar 20 2023 11:32:23
%S A199113 6,17,50,149,446,1337,4010,12029,36086,108257,324770,974309,2922926,
%T A199113 8768777,26306330,78918989,236756966,710270897,2130812690,6392438069,
%U A199113 19177314206,57531942617,172595827850,517787483549,1553362450646,4660087351937
%N A199113 a(n) = (11*3^n+1)/2.
%H A199113 Vincenzo Librandi, <a href="/A199113/b199113.txt">Table of n, a(n) for n = 0..1000</a>
%H A199113 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,-3).
%F A199113 a(n) = 3*a(n-1)-1.
%F A199113 a(n) = 4*a(n-1)-3*a(n-2).
%F A199113 G.f.: (6-7*x)/((1-x)*(1-3*x)). - _Bruno Berselli_, Nov 04 2011
%t A199113 LinearRecurrence[{4,-3},{6,17},30] (* or *) (11 3^Range[0,30]+1)/2 (* _Harvey P. Dale_, Mar 25 2012 *)
%o A199113 (Magma) [(11*3^n+1)/2: n in [0..30]];
%K A199113 nonn,easy
%O A199113 0,1
%A A199113 _Vincenzo Librandi_, Nov 04 2011