设数列(An)满足An+1=An^ - nAn + 1 n=1,2,3,4..... 当A1大于等于3时 证明对所有的n大于等于1有(1)An大于等于n+2(2)1/1+A1 + 1/1+A2 + 1/1+A3 +.....+ 1/1+An设数列{an}满足an+1=an^2-nan+1,n为正整数,当a1>=3时, 证明(1)an>=n+2(2)1/(1+a1) + 1/(1+a2) + ……+1/(1+an) =< 1/2