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 A355088 #8 Jun 18 2022 14:14:02
%S A355088 1,1,7,199,21883,8916991,13027669147,66525761289919,
%T A355088 1164200761777844203,68750129286493392353311,
%U A355088 13532431689375421261723713787,8789916574829303798007959322784639,18685340957126032386127459367999667264523
%N A355088 E.g.f. A(x) satisfies A(x) = 1 + (exp(x) - 1) * A(3*x).
%F A355088 a(0) = 1; a(n) = Sum_{k=0..n-1} 3^k * binomial(n,k) * a(k).
%o A355088 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=0, i-1, 3^j*binomial(i, j)*v[j+1])); v;
%Y A355088 Cf. A000670, A352860.
%Y A355088 Cf. A355085, A355087.
%K A355088 nonn
%O A355088 0,3
%A A355088 _Seiichi Manyama_, Jun 18 2022