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 A367657 #8 Nov 26 2023 08:37:42
%S A367657 1,2,5,13,34,90,238,629,1662,4394,11616,30707,81173,214584,567259,
%T A367657 1499563,3964128,10479273,27702219,73231500,193589270,511758023,
%U A367657 1352844978,3576279113,9453982143,24991835308,66066533905,174648514118,461687660561,1220482733670
%N A367657 G.f. A(x) satisfies A(x) = 1 / (1 - x - x * (1 + x + x^2 + x^3) * A(x^4)).
%F A367657 a(0) = 1; a(n) = a(n-1) + Sum_{k=0..n-1} a(floor(k/4)) * a(n-1-k).
%o A367657 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=v[i]+sum(j=0, i-1, v[j\4+1]*v[i-j])); v;
%Y A367657 Cf. A367655, A367656, A367658.
%Y A367657 Cf. A367653, A367660.
%K A367657 nonn
%O A367657 0,2
%A A367657 _Seiichi Manyama_, Nov 26 2023