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 A187890 #29 Jul 22 2024 09:47:26
%S A187890 0,4,3,6,8,13,20,32,51,82,132,213,344,556,899,1454,2352,3805,6156,
%T A187890 9960,16115,26074,42188,68261,110448,178708,289155,467862,757016,
%U A187890 1224877,1981892,3206768,5188659,8395426,13584084,21979509,35563592,57543100
%N A187890 a(1) = 0, a(2) = 4, a(n) = a(n-1) + a(n-2) - 1.
%H A187890 Vincenzo Librandi, <a href="/A187890/b187890.txt">Table of n, a(n) for n = 1..1000</a>
%H A187890 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-1).
%F A187890 G.f.: -x^2*(-4+5*x) / ( (x-1)*(x^2+x-1) ). - _R. J. Mathar_, Mar 15 2011
%F A187890 a(n) = 1+A001060(n-2), n>2. - _R. J. Mathar_, Mar 15 2011
%F A187890 a(n) - a(n-1) = A013655(n-4). - _R. J. Mathar_, Jun 19 2021
%F A187890 If we start the sequence 1, 3, 6, ... and set the offset to 0, then the sequence has the generating function (1 + x - 3*x^3)/(x^3 - 2*x + 1) and gives the row sums of A374438. - _Peter Luschny_, Jul 22 2024
%t A187890 Join[{a = 0, b = 4}, Table[c = a+b-1; a=b; b=c, {n, 100}]]
%t A187890 LinearRecurrence[{2, 0, -1}, {0, 4, 3}, 40] (* _Harvey P. Dale_, Sep 25 2013 *)
%t A187890 CoefficientList[Series[(-x (-4 + 5 x))/((x - 1) (x^2 + x - 1)), {x, 0, 40}], x] (* _Vincenzo Librandi_, Sep 26 2013 *)
%Y A187890 Cf. A000071, A001611, A001612, A374438.
%K A187890 nonn,easy
%O A187890 1,2
%A A187890 _Vladimir Joseph Stephan Orlovsky_, Mar 15 2011
%E A187890 Definition adapted to offset by _Georg Fischer_, Jun 19 2021