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 A367659 #13 Nov 27 2023 10:48:29
%S A367659 1,2,4,8,18,40,88,196,436,968,2152,4784,10632,23634,52536,116776,
%T A367659 259576,577000,1282576,2850968,6337264,14086744,31312644,69603152,
%U A367659 154716976,343911796,764462500,1699281320,3777238312,8396213840,18663478600,41486012712,92216959616
%N A367659 G.f. A(x) satisfies A(x) = 1 / (1 - x - x * A(x^3)).
%H A367659 Seiichi Manyama, <a href="/A367659/b367659.txt">Table of n, a(n) for n = 0..1000</a>
%F A367659 a(0) = 1; a(n) = a(n-1) + Sum_{k=0..floor((n-1)/3)} a(k) * a(n-1-3*k).
%F A367659 a(0) = 1, a(1) = 2, a(2) = 4; a(n) = a(n-3) + Sum_{k=0..n-1} a(floor(k/3)) * a(n-1-k).
%o A367659 (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)\3, v[j+1]*v[i-3*j])); v;
%Y A367659 Cf. A349365, A367660, A367661.
%K A367659 nonn
%O A367659 0,2
%A A367659 _Seiichi Manyama_, Nov 26 2023