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 A367973 #8 Dec 07 2023 08:27:15
%S A367973 1,3,14,89,727,7322,88067,1233815,19745180,355434387,7108803715,
%T A367973 156394360300,3753468860797,97590218025159,2732526295603774,
%U A367973 81975790251071765,2623225298514438627,89189660232355783122
%N A367973 Expansion of e.g.f. exp(exp(x) - 1)/(1 - 2*x).
%F A367973 a(0) = 1; a(n) = Sum_{k=1..n} (2^k * (k-1)! + 1) * binomial(n-1,k-1) * a(n-k).
%F A367973 a(n) = n! * Sum_{k=0..n} 2^(n-k) * Bell(k)/k!, where Bell() is A000110.
%o A367973 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=1, i, (2^j*(j-1)!+1)*binomial(i-1, j-1)*v[i-j+1])); v;
%Y A367973 Cf. A000110, A367972.
%K A367973 nonn,easy
%O A367973 0,2
%A A367973 _Seiichi Manyama_, Dec 06 2023