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 A367661 #13 Nov 27 2023 10:48:33
%S A367661 1,2,4,8,16,32,66,136,280,576,1184,2436,5012,10312,21216,43648,89800,
%T A367661 184752,380104,782016,1608896,3310096,6810096,14010896,28825616,
%U A367661 59304992,122012384,251024768,516451136,1062531712,2186022176,4497459138,9252943048
%N A367661 G.f. A(x) satisfies A(x) = 1 / (1 - x - x * A(x^5)).
%H A367661 Seiichi Manyama, <a href="/A367661/b367661.txt">Table of n, a(n) for n = 0..1000</a>
%F A367661 a(0) = 1; a(n) = a(n-1) + Sum_{k=0..floor((n-1)/5)} a(k) * a(n-1-5*k).
%F A367661 a(0) = 1, a(1) = 2, a(2) = 4, a(3) = 8, a(4) = 16; a(n) = a(n-5) + Sum_{k=0..n-1} a(floor(k/5)) * a(n-1-k).
%o A367661 (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)\5, v[j+1]*v[i-5*j])); v;
%Y A367661 Cf. A349365, A367659, A367660.
%K A367661 nonn
%O A367661 0,2
%A A367661 _Seiichi Manyama_, Nov 26 2023