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 A368453 #10 Dec 25 2023 09:59:29
%S A368453 1,2,8,52,452,4892,63508,962012,16654772,324375292,7019618708,
%T A368453 167098274972,4339293330292,122075401356092,3698469101172308,
%U A368453 120054668185331932,4156854586083305012,152925374174876071292,5956866331612558316308,244927333201908131524892
%N A368453 Expansion of e.g.f. 3*exp(x) / (4 - exp(3*x)).
%F A368453 a(n) = 1 + Sum_{k=1..n} 3^(k-1) * binomial(n,k) * a(n-k).
%o A368453 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+sum(j=1, i, 3^(j-1)*binomial(i, j)*v[i-j+1])); v;
%Y A368453 Cf. A151919, A368440, A368441.
%Y A368453 Cf. A368450.
%K A368453 nonn
%O A368453 0,2
%A A368453 _Seiichi Manyama_, Dec 24 2023