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 A159285 #22 Mar 23 2023 06:21:52
%S A159285 1,3,1,5,7,7,17,21,31,55,73,117,183,263,417,629,943,1463,2201,3349,
%T A159285 5127,7751,11825,18005,27327,41655,63337,96309,146647,222983,339265,
%U A159285 516277,785231,1194807,1817785,2765269,4207399,6400839,9737937,14815637
%N A159285 Expansion of (1+3*x)/(1-x^2-2*x^3).
%C A159285 A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj')
%H A159285 G. C. Greubel, <a href="/A159285/b159285.txt">Table of n, a(n) for n = 0..1000</a>
%H A159285 Creighton Dement, <a href="http://fumba.eu/sitelayout/Floretion.php">Online Floretion Multiplier</a> [broken link]
%H A159285 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,2).
%F A159285 a(n) = A052947(n) + 3*A052947(n-1). - _R. J. Mathar_, Mar 23 2023
%t A159285 LinearRecurrence[{0, 1, 2}, {1, 3, 1}, 50] (* _G. C. Greubel_, Jun 27 2018 *)
%t A159285 CoefficientList[Series[(1+3x)/(1-x^2-2x^3),{x,0,40}],x] (* _Harvey P. Dale_, Jan 21 2019 *)
%o A159285 (PARI) a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[1;3;1])[1,1] \\ _Charles R Greathouse IV_, Oct 03 2016
%o A159285 (Magma) I:=[1,3,1]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-3): n in [1..30]]; // _G. C. Greubel_, Jun 27 2018
%Y A159285 Cf. A159284, A159286, A159287, A159288.
%K A159285 easy,nonn
%O A159285 0,2
%A A159285 _Creighton Dement_, Apr 08 2009