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 A168609 #26 Mar 11 2023 15:39:05
%S A168609 5,7,13,31,85,247,733,2191,6565,19687,59053,177151,531445,1594327,
%T A168609 4782973,14348911,43046725,129140167,387420493,1162261471,3486784405,
%U A168609 10460353207,31381059613,94143178831,282429536485,847288609447
%N A168609 a(n) = 3^n + 4.
%H A168609 Vincenzo Librandi, <a href="/A168609/b168609.txt">Table of n, a(n) for n = 0..1000</a>
%H A168609 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,-3).
%F A168609 a(n) = 3*a(n-1) - 8, with n>0, a(0)=5.
%F A168609 G.f.: (5 - 13*x)/((1-x)*(1-3 x)). - _Vincenzo Librandi_, May 13 2014
%F A168609 a(n) = 4*a(n-1) - 3*a(n-2) for n>1. - _Vincenzo Librandi_, May 13 2014
%F A168609 E.g.f.: exp(3*x) + 4*exp(x). - _G. C. Greubel_, Jul 27 2016
%e A168609 a(1)=3*5-8=7; a(2)=3*7-8=13; a(3)=3*13-8=31.
%t A168609 Table[3^n + 4, {n, 0, 50}] (* _Vladimir Joseph Stephan Orlovsky_, May 19 2011 *)
%t A168609 CoefficientList[Series[(5 - 13 x)/((1 - x) (1 - 3 x)), {x, 0, 30}], x] (* _Vincenzo Librandi_, May 13 2014 *)
%t A168609 LinearRecurrence[{4,-3},{5,7},30] (* _Harvey P. Dale_, Mar 11 2023 *)
%o A168609 (Magma) [3^n+4: n in [0..30]]; // _Vincenzo Librandi_, May 13 2014
%Y A168609 Cf. A034472, A168607, A168610, A178674.
%K A168609 nonn,easy
%O A168609 0,1
%A A168609 _Vincenzo Librandi_, Dec 01 2009
%E A168609 Formula and examples edited to use correct offset by _Jon E. Schoenfield_, Jun 19 2010