exp[1/(1-z)]=exp[(0到∞)∑(z^n)] =exp(1+z+z^2+z^3+…) =e*e^z*e^(z^2)*e^(z^3)*… =e*(1+z/1!+z^2/2!+z^3/3!+z^4/4!+…)*(1+z^2/1!+z^4/2!+…)*(1+z^3/1!+…)*(1+z^4/1!+…)*… =e(1+z/1!+3z^2/2!+13z^3/3!+73z^4...