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 A355073 #14 Jun 18 2022 14:00:04
%S A355073 1,1,4,55,2539,383860,187659181,293630900689,1459799672901004,
%T A355073 22924423319469919651,1131844225175191511724871,
%U A355073 175015470856131731421651730600,84480805958219938739735661779357401,126948830401157131161305967764668449231937
%N A355073 G.f.: Sum_{n>=0} a(n)*x^n/(n!*3^(n*(n-1)/2)) = exp( Sum_{n>=1} x^n/(n!*3^(n*(n-1)/2)) ).
%o A355073 (PARI) a(n) = n!*3^(n*(n-1)/2)*polcoef(exp(sum(k=1, n, x^k/(k!*3^(k*(k-1)/2)))+x*O(x^n)), n);
%o A355073 (PARI) T(n, k) = if(k==1, 1, sum(j=1, n-1, 3^(j*(n-j))*binomial(n-1, j)*T(j, k-1)));
%o A355073 a(n) = if(n==0, 1, sum(k=1, n, T(n, k)));
%Y A355073 Cf. A000110, A240936, A355074.
%Y A355073 Cf. A355070, A355081.
%K A355073 nonn
%O A355073 0,3
%A A355073 _Seiichi Manyama_, Jun 18 2022