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 A155204 #4 Jun 15 2025 04:10:32
%S A155204 1,4,58,7528,11333974,173018964568,25223063625377572,
%T A155204 34295288559321731710864,429734241619476967064512081894,
%U A155204 49292144502053186639397817183561560472
%N A155204 G.f.: A(x) = exp( Sum_{n>=1} (3^n + 1)^n * x^n/n ), a power series in x with integer coefficients.
%C A155204 More generally, for m integer, exp( Sum_{n>=1} (m^n + y)^n * x^n/n ) is a power series in x and y with integer coefficients.
%F A155204 Equals row sums of triangle A155812.
%e A155204 G.f.: A(x) = 1 + 4*x + 58*x^2 + 7528*x^3 + 11333974*x^4 + 173018964568*x^5 +...
%e A155204 log(A(x)) = 4*x + 10^2*x^2/2 + 28*x^3/3 + 82^4*x^4/4 + 244^5*x^5/5 +...
%o A155204 (PARI) {a(n)=polcoeff(exp(sum(m=1,n+1,(3^m+1)^m*x^m/m)+x*O(x^n)),n)}
%Y A155204 Cf. A155203, A155205, A155206, A155812 (triangle), A202989; variants: A155201, A155208.
%K A155204 nonn
%O A155204 0,2
%A A155204 _Paul D. Hanna_, Feb 04 2009