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 A155205 #4 Jun 15 2025 04:12:51
%S A155205 1,2,34,5924,10252294,166020197708,24810918565918804,
%T A155205 34076399079565985138408,428687477154543524080261047622,
%U A155205 49247086840315416213775472777558582540
%N A155205 G.f.: A(x) = exp( Sum_{n>=1} (3^n - 1)^n * x^n/n ), a power series in x with integer coefficients.
%C A155205 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.
%e A155205 G.f.: A(x) = 1 + 2*x + 34*x^2 + 5924*x^3 + 10252294*x^4 +...
%e A155205 log(A(x)) = 2*x + 8^2*x^2/2 + 26^3*x^3/3 + 80^4*x^4/4 + 242^5*x^5/5 +...
%o A155205 (PARI) {a(n)=polcoeff(exp(sum(m=1,n+1,(3^m-1)^m*x^m/m)+x*O(x^n)),n)}
%Y A155205 Cf. A060613, A155203, A155204, A155206, A155812 (triangle), variants: A155202, A155209.
%K A155205 nonn
%O A155205 0,2
%A A155205 _Paul D. Hanna_, Feb 04 2009