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 A140504 #36 Nov 11 2023 19:56:05
%S A140504 5,6,8,12,20,36,68,132,260,516,1028,2052,4100,8196,16388,32772,65540,
%T A140504 131076,262148,524292,1048580,2097156,4194308,8388612,16777220,
%U A140504 33554436,67108868,134217732,268435460,536870916,1073741828
%N A140504 a(n) = 2^n + 4.
%H A140504 G. C. Greubel, <a href="/A140504/b140504.txt">Table of n, a(n) for n = 0..1000</a>
%H A140504 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2).
%F A140504 G.f.: (5 - 9*x)/((1 - x)*(1 - 2*x)). - _Jaume Oliver Lafont_, Aug 30 2009
%F A140504 a(n) = 2*a(n-1) - 4 with a(0) = 5. - _Vincenzo Librandi_, Nov 24 2009
%F A140504 From _Reinhard Zumkeller_, Feb 28 2010: (Start)
%F A140504 a(n) = A173786(n,2) for n > 1.
%F A140504 a(n+2)*A028399(n) = A175164(2*n). (End)
%F A140504 From _G. C. Greubel_, Jul 08 2021: (Start)
%F A140504 a(n) = m*(2^(n-2) + 1), with m = 4.
%F A140504 E.g.f.: exp(2*x) + 4*exp(x). (End)
%t A140504 Table[2^n + 4, {n, 0, 30}] (* _Stefan Steinerberger_, Aug 04 2008 *)
%t A140504 LinearRecurrence[{3,-2}, {5,6}, 40] (* _Harvey P. Dale_, May 26 2018 *)
%o A140504 (Sage) [2^n + 4 for n in range(0,31)] # _Zerinvary Lajos_, May 31 2009
%o A140504 (PARI) a(n)=2^n+4 \\ _Charles R Greathouse IV_, Dec 21 2011
%o A140504 (Magma) [2^n +4: n in [0..30]]; // _G. C. Greubel_, Jul 08 2021
%Y A140504 Cf. A000051 (m=0), A052548 (m=2), this sequence (m=4), A153973 (m=6), A231643 (m=5), A175161 (m=8), A175162 (m=16), A175163 (m=32).
%K A140504 nonn,easy
%O A140504 0,1
%A A140504 _Paul Curtz_, Jun 30 2008
%E A140504 More terms from _Stefan Steinerberger_, Aug 04 2008