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 A168613 #23 Sep 12 2022 17:01:14
%S A168613 -4,-2,4,22,76,238,724,2182,6556,19678,59044,177142,531436,1594318,
%T A168613 4782964,14348902,43046716,129140158,387420484,1162261462,3486784396,
%U A168613 10460353198,31381059604,94143178822,282429536476,847288609438
%N A168613 a(n) = 3^n - 5.
%H A168613 Vincenzo Librandi, <a href="/A168613/b168613.txt">Table of n, a(n) for n = 0..1000</a>
%H A168613 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,-3).
%F A168613 a(n) = 3*a(n-1) + 10 with a(0)=-4.
%F A168613 G.f.: 2*(7*x - 2)/((1-x)*(1-3*x)). - _Vincenzo Librandi_, Jul 06 2012
%F A168613 a(n) = 4*a(n-1) - 3*a(n-2). - _Vincenzo Librandi_, Jul 06 2012
%F A168613 a(n) = 2*A116970(n) + 2 with A116970(0)=-3, A116970(1)=-2. - _Bruno Berselli_, Jul 06 2012
%F A168613 E.g.f.: exp(3*x) - 5*exp(x). - _G. C. Greubel_, Jul 27 2016
%t A168613 CoefficientList[Series[2*(7*x-2)/((1-x)*(1-3*x)),{x,0,40}],x] (* _Vincenzo Librandi_, Jul 06 2012 *)
%t A168613 LinearRecurrence[{4,-3}, {-4, -2}, 25] (* _G. C. Greubel_, Jul 27 2016 *)
%t A168613 3^Range[0,30]-5 (* _Harvey P. Dale_, Sep 12 2022 *)
%o A168613 (Magma) I:=[-4, -2]; [n le 2 select I[n] else 4*Self(n-1)-3*Self(n-2): n in [1..30]]; // _Vincenzo Librandi_, Jul 06 2012
%Y A168613 Cf. A168610.
%K A168613 sign,easy
%O A168613 0,1
%A A168613 _Vincenzo Librandi_, Dec 01 2009
%E A168613 Formula and examples edited to use correct offset by _Jon E. Schoenfield_, Jun 19 2010