解答题-问答题 适中0.65 引用2 组卷1019
数列{an}中,a1=1,当
时,其前n项和满足
.
(Ⅰ)求Sn的表达式;
(Ⅱ)设
,数列{bn}的前n项和为
,求
.
![](https://img.xkw.com/dksih/QBM/2014/1/13/1571477380866048/1571477386616832/STEM/c5221c6884c440ad99c8517ac9eea169.png)
![](https://img.xkw.com/dksih/QBM/2014/1/13/1571477380866048/1571477386616832/STEM/01c61cd9de6b46f99c78537852499e98.png)
(Ⅰ)求Sn的表达式;
(Ⅱ)设
![](https://img.xkw.com/dksih/QBM/2014/1/13/1571477380866048/1571477386616832/STEM/d4739e61c7f345a2b7ca1966fe66bb07.png)
![](https://img.xkw.com/dksih/QBM/2014/1/13/1571477380866048/1571477386616832/STEM/4f90517f88144128aad383b8cd657c50.png)
![](https://img.xkw.com/dksih/QBM/2014/1/13/1571477380866048/1571477386616832/STEM/4f90517f88144128aad383b8cd657c50.png)
2013·陕西咸阳·一模
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