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 A130844 #22 Sep 08 2022 08:45:30
%S A130844 0,3,5,17,36,87,198,464,1075,2503,5815,13522,31431,73072,169868,
%T A130844 394899,918025,2134153,4961300,11533627,26812426,62331332,144902763,
%U A130844 336858059,783099975,1820486578,4232117835,9838480332,22871691896,53170232867
%N A130844 a(n) = 2*a(n-1) + a(n-2) - a(n-3) + a(n-4), with a(1) = 0, a(2) = 3, a(3) = 5 and a(4) = 17.
%H A130844 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,1,-1,1).
%F A130844 G.f.: x^2*(3 - x + 4*x^2)/((1 + x)*(1 - 3*x + 2*x^2 - x^3)). - _Colin Barker_, Nov 02 2012
%t A130844 LinearRecurrence[{2,1,-1,1},{0,3,5,17},30] (* _Harvey P. Dale_, Dec 20 2014 *)
%o A130844 (PARI) m=30; v=concat([0,3,5,17], vector(m-4)); for(n=5, m, v[n] = 2*v[n-1] +v[n-2] -v[n-3] +v[n-4]); v \\ _G. C. Greubel_, Nov 03 2018
%o A130844 (Magma) I:=[0,3,5,17]; [n le 4 select I[n] else 2*Self(n-1) +Self(n-2) -Self(n-3) + Self(n-4): n in [1..30]]; // _G. C. Greubel_, Nov 03 2018
%Y A130844 Cf. A107479, A107480, A109538, A109543, A109544, A114749, A125950, A143335, A147851.
%K A130844 nonn,easy
%O A130844 1,2
%A A130844 _Roger L. Bagula_, Jul 20 2007
%E A130844 New name (after _Colin Barker_) by _Franck Maminirina Ramaharo_, Nov 02 2018
%E A130844 Edited by _N. J. A. Sloane_, Nov 03 2018