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 A135583 #22 Feb 27 2024 03:02:47
%S A135583 3,8,28,108,428,1708,6828,27308,109228,436908,1747628,6990508,
%T A135583 27962028,111848108,447392428,1789569708,7158278828,28633115308,
%U A135583 114532461228,458129844908,1832519379628,7330077518508,29320310074028
%N A135583 a(n) = 4*a(n-1) - 4 for n>0, a(0)=3.
%H A135583 Vincenzo Librandi, <a href="/A135583/b135583.txt">Table of n, a(n) for n = 0..1000</a>
%H A135583 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,-4).
%F A135583 From _R. J. Mathar_, Mar 31 2008: (Start)
%F A135583 a(n) = (4 + 5*4^n)/3.
%F A135583 a(n) - a(n-1) = A003947(n).
%F A135583 O.g.f.: (3 - 7*x)/((1 - x)*(1 - 4*x)). (End)
%F A135583 a(0)=3, a(1)=8; for n>1, a(n) = 5*a(n-1) - 4*a(n-2). - _Harvey P. Dale_, Feb 27 2013
%F A135583 E.g.f.: (1/3)*(4*exp(x) + 5*exp(4*x)). - _G. C. Greubel_, Oct 20 2016
%t A135583 NestList[4#-4&,3,30] (* or *) LinearRecurrence[{5,-4},{3,8},30] (* _Harvey P. Dale_, Feb 27 2013 *)
%o A135583 (Magma) [(4+5*4^n)/3: n in [0..30]]; // _Vincenzo Librandi_, Aug 10 2011
%Y A135583 Cf. A003947.
%K A135583 nonn,easy
%O A135583 0,1
%A A135583 _Paul Curtz_, Feb 25 2008
%E A135583 More terms from _R. J. Mathar_, Mar 31 2008