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 A367656 #9 Nov 26 2023 08:38:18
%S A367656 1,2,5,13,35,94,252,678,1823,4900,13176,35427,95250,256105,688599,
%T A367656 1851450,4978062,13384681,35987808,96761612,260166110,699517054,
%U A367656 1880814358,5057006914,13596939262,36558534049,98296122593,264291989596,710610490247,1910641595588
%N A367656 G.f. A(x) satisfies A(x) = 1 / (1 - x - x * (1 + x + x^2) * A(x^3)).
%F A367656 a(0) = 1; a(n) = a(n-1) + Sum_{k=0..n-1} a(floor(k/3)) * a(n-1-k).
%o A367656 (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\3+1]*v[i-j])); v;
%Y A367656 Cf. A367655, A367657, A367658.
%Y A367656 Cf. A367652, A367659.
%K A367656 nonn
%O A367656 0,2
%A A367656 _Seiichi Manyama_, Nov 26 2023