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 A199560 #16 Sep 14 2024 15:51:08
%S A199560 2,14,122,1094,9842,88574,797162,7174454,64570082,581130734,
%T A199560 5230176602,47071589414,423644304722,3812798742494,34315188682442,
%U A199560 308836698141974,2779530283277762,25015772549499854,225141952945498682,2026277576509488134,18236498188585393202
%N A199560 a(n) = (3*9^n + 1)/2.
%H A199560 Vincenzo Librandi, <a href="/A199560/b199560.txt">Table of n, a(n) for n = 0..1000</a>
%H A199560 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (10,-9).
%F A199560 a(n) = 2*A066443(n).
%F A199560 a(n) = 9*a(n-1) - 4.
%F A199560 a(n) = 10*a(n-1) - 9*a(n-2).
%F A199560 G.f.: 2*(1-3*x)/((1-x)*(1-9*x)).
%F A199560 From _Elmo R. Oliveira_, Sep 13 2024: (Start)
%F A199560 E.g.f.: exp(x)*(3*exp(8*x) + 1)/2.
%F A199560 a(n) = A199561(n)/2. (End)
%t A199560 LinearRecurrence[{10,-9},{2,14},30] (* or *) NestList[9#-4&,2,30] (* _Harvey P. Dale_, May 30 2012 *)
%o A199560 (Magma) [(3*9^n+1)/2: n in [0..30]];
%Y A199560 Cf. A066443, A199561.
%K A199560 nonn,easy
%O A199560 0,1
%A A199560 _Vincenzo Librandi_, Nov 08 2011