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 A368441 #10 Dec 25 2023 10:02:07
%S A368441 1,10,208,6508,271468,14154580,885638908,64649204308,5393387534428,
%T A368441 506188870889140,52786278954586108,6055112126576175508,
%U A368441 757725480419984012188,102722055234542078115700,14996854976334688765608508,2345848207305916218955201108
%N A368441 Expansion of e.g.f. exp(x) / (4 - 3*exp(3*x)).
%F A368441 a(n) = 1 + 3 * Sum_{k=1..n} 3^k * binomial(n,k) * a(n-k).
%o A368441 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+3*sum(j=1, i, 3^j*binomial(i, j)*v[i-j+1])); v;
%Y A368441 Cf. A151919, A368440, A368453.
%K A368441 nonn
%O A368441 0,2
%A A368441 _Seiichi Manyama_, Dec 24 2023