面对进入青春期的生理变化,我们应( )
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(Ⅰ)求{an}的通项公式;
(Ⅱ)求{an}的前n项和Sn及使得Sn最大的序号n的值.
The story of Lei Haiwei, the winner of The Poetry Conference(诗词大会), again proved that it's necessary not to ____.