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 A367717 #9 Nov 28 2023 08:50:56
%S A367717 1,0,2,2,5,8,16,30,57,108,206,390,741,1407,2670,5068,9622,18262,34666,
%T A367717 65806,124911,237109,450092,854368,1621784,3078519,5843709,11092672,
%U A367717 21056400,39969753,75871567,144021302,273384733,518945611,985075356,1869894158,3549478993
%N A367717 G.f. A(x) satisfies A(x) = 1 / ((1 + x) * (1 - x * (1 + x + x^2) * A(x^3))).
%F A367717 a(n) = (-1)^n + Sum_{k=0..n-1} a(floor(k/3)) * a(n-1-k).
%o A367717 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=(-1)^i+sum(j=0, i-1, v[j\3+1]*v[i-j])); v;
%Y A367717 Cf. A005043, A367716, A367718.
%Y A367717 Cf. A367693, A367714.
%K A367717 nonn
%O A367717 0,3
%A A367717 _Seiichi Manyama_, Nov 28 2023