根据二项式定理,有
[1+(1/n)]^n
=1+n*(1/n)+[n*(n-1)/(2!)]*[(1/n)^2]+...+[n*...*1/(n!)]*[((1/n)^n]
=1+1+[n*(n-1)/(2!)]*[(1/n)^2]+...+[n*...*1/(n!)]*[(1/n)^n]
而对任意2