1/2!+2/3!+3/4!+……n/(n+1)! =(1/1-1/2!)+(1/2!-1/3!)+(1/3!-1/4!)+...+[1/n!-1/(n+1)!]=1-1/(n+1)!
n/(n+1)! =[(n+1)-1]/(n+1)!=1/n! - 1/(n+1)!1/2!+2/3!+3/4!+……+n/(n+1)!=(1/1!-1/2!)+(1/2! -1/3!)+……+[1/n! - 1/(n+1)!]=1/1! -1/(n+1)!=1-1/(n+1)!
与自然对数有关。