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 A251656 #33 Mar 28 2025 10:13:23
%S A251656 1,0,1,0,2,3,6,11,22,42,81,156,301,580,1118,2155,4154,8007,15434,
%T A251656 29750,57345,110536,213065,410696,791642,1525939,2941342,5669619,
%U A251656 10928542,21065442,40604945,78268548,150867477,290806412,560547382,1080489819
%N A251656 4-step Fibonacci sequence starting with 1,0,1,0.
%H A251656 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,1,1).
%F A251656 a(n+4) = a(n)+a(n+1)+a(n+2)+a(n+3).
%F A251656 G.f.: (-1+x+2*x^3)/(-1+x+x^2+x^3+x^4) . - _R. J. Mathar_, Mar 28 2025
%F A251656 a(n) = A000078(n+3)-A000078(n+2)-2*A000078(n). - _R. J. Mathar_, Mar 28 2025
%t A251656 LinearRecurrence[Table[1, {4}], {1, 0, 1, 0}, 36] (* _Michael De Vlieger_, Dec 09 2014 *)
%o A251656 (J) NB. see A251655 for the program and apply it to 1,0,1,0.
%Y A251656 Other 4-step Fibonacci sequences are A000078, A000288, A001630, A001631, A001648, A073817, A100532, A251654, A251655, A251703, A251704, A251705.
%Y A251656 Cf. A000336.
%K A251656 nonn,easy
%O A251656 0,5
%A A251656 _Arie Bos_, Dec 06 2014