设数列{an}的前n项和为Sn,a1=1,Sn=nan-2n(n-1).(1)求数列{an}的通项公式;(2)设数列{1/(ana(n+1))}的前n项和为Tn,求证:0.2≦Tn≤0.25
问题描述:
设数列{an}的前n项和为Sn,a1=1,Sn=nan-2n(n-1).(1)求数列{an}的通项公式;(2)设数列{1/(ana(n+1))}的前n项和为Tn,求证:0.2≦Tn≤0.25
答
设数列{an}的前n项和为Sn,a1=1,Sn=nan-2n(n-1).(1)求数列{an}的通项公式;(2)设数列{1/(ana(n+1))}的前n项和为Tn,求证:0.2≦Tn≤0.25