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 A368440 #10 Dec 25 2023 10:02:11
%S A368440 1,7,103,2287,67687,2504047,111163303,5757411247,340788559207,
%T A368440 22693176094447,1679047763217703,136654363293340207,
%U A368440 12133120656211741927,1167034341869994747247,120886955198779063694503,13416476227330202250197167,1588276885073067052758303847
%N A368440 Expansion of e.g.f. exp(x) / (3 - 2*exp(3*x)).
%F A368440 a(n) = 1 + 2 * Sum_{k=1..n} 3^k * binomial(n,k) * a(n-k).
%o A368440 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+2*sum(j=1, i, 3^j*binomial(i, j)*v[i-j+1])); v;
%Y A368440 Cf. A151919, A368441, A368453.
%K A368440 nonn
%O A368440 0,2
%A A368440 _Seiichi Manyama_, Dec 24 2023