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 A135078 #2 Mar 30 2012 18:37:07
%S A135078 1,1,4,46,1519,145795,41134753,34354750885,85260288495316,
%T A135078 630102185300832652,13884412839047621240875,
%U A135078 912975607895806507921828357,179255108346123463104458490745825
%N A135078 E.g.f. A(x) = 1 + Sum_{n>=1} (1/n!)*Product_{k=0..n-1} [exp(3^k*x) - 1].
%e A135078 A(x) = 1 + x + 4x^2/2! + 46x^3/3! + 1519x^4/4! + 145795x^5/5! +...;
%e A135078 A(x) = 1 + [exp(x)-1] + [exp(x)-1][exp(3x)-1]/2! + [exp(x)-1][exp(3x)-1][exp(9x)-1]/3! + [exp(x)-1][exp(3x)-1][exp(9x)-1][exp(27x)-1]/4! +...
%o A135078 (PARI) {a(n)=n!*polcoeff(1+sum(j=1,n,(1/j!)*prod(k=0,j-1,1*exp(3^k*x)-1)),n)}
%Y A135078 Cf. variants: A135077, A135079.
%K A135078 nonn
%O A135078 0,3
%A A135078 _Paul D. Hanna_, Nov 24 2007