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 A153873 #28 Jan 03 2024 08:46:47
%S A153873 8,17,44,116,305,800,2096,5489,14372,37628,98513,257912,675224,
%T A153873 1767761,4628060,12116420,31721201,83047184,217420352,569213873,
%U A153873 1490221268,3901449932,10214128529,26740935656,70008678440,183285099665,479846620556,1256254762004,3288917665457
%N A153873 a(n) = 9*Fibonacci(2n+1) - 1.
%H A153873 Vincenzo Librandi, <a href="/A153873/b153873.txt">Table of n, a(n) for n = 0..200</a>
%H A153873 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,-4,1).
%F A153873 a(n) = 3*a(n-1) - a(n-2) + 1.
%F A153873 a(n) = 4*a(n-1) - 4*a(n-2) + a(n-3).
%F A153873 a(n) = 3*a(n-1) - 3*a(n-3) + a(n-4).
%F A153873 a(n) = 9*A001519(n+1) - 1.
%F A153873 G.f.: (8 - 15*x + 8*x^2)/((1-x)*(1-3*x+x^2)). - _Jaume Oliver Lafont_, Aug 30 2009
%t A153873 LinearRecurrence[{4,-4,1}, {8,17,44}, 25] (* _G. C. Greubel_, Aug 31 2016 *)
%o A153873 (Magma) [9*Fibonacci(2*n+1)-1: n in [0..30]]; // _Vincenzo Librandi_, Aug 07 2011
%o A153873 (PARI) a(n)=9*fibonacci(2*n+1)-1 \\ _Charles R Greathouse IV_, Oct 07 2015
%K A153873 nonn,easy
%O A153873 0,1
%A A153873 _Paul Curtz_, Jan 03 2009