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 A251703 #28 Mar 28 2025 10:19:34
%S A251703 1,1,0,0,2,3,5,10,20,38,73,141,272,524,1010,1947,3753,7234,13944,
%T A251703 26878,51809,99865,192496,371048,715218,1378627,2657389,5122282,
%U A251703 9873516,19031814,36685001,70712613,136302944,262732372,506432930,976180859
%N A251703 4-step Fibonacci sequence starting with 1,1,0,0.
%H A251703 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,1,1).
%F A251703 a(n+4) = a(n) + a(n+1) + a(n+2) + a(n+3).
%F A251703 G.f.: (-1+2*x^2+2*x^3)/(-1+x+x^2+x^3+x^4) . - _R. J. Mathar_, Mar 28 2025
%F A251703 a(n) = A000078(n+3)-2*A000078(n+1)-2*A000078(n). - _R. J. Mathar_, Mar 28 2025
%t A251703 LinearRecurrence[Table[1, {4}], {1, 1, 0, 0}, 36] (* _Michael De Vlieger_, Dec 09 2014 *)
%o A251703 (J) NB. see A251655 for the program and apply it to 1,1,0,0.
%Y A251703 Other 4-step Fibonacci sequences are A000078, A000288, A001630, A001631, A001648, A073817, A100532, A251654, A251655, A251656, A251704, A251705.
%K A251703 nonn,easy
%O A251703 0,5
%A A251703 _Arie Bos_, Dec 07 2014