题目内容
已知数列
的通项公式为
,将此数列中的各项分组如下:第一组:
;第二组:
;……;如果第
组的最后一个数为
,那么第
组的
个数依次排列为:![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130832510.gif)
,(
).则第6组的第一个数是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130582376.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130598428.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130614206.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130629355.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130707198.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130723316.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130754233.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130785206.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130832510.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130848361.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130879441.gif)
A.61 | B.81 | C.125 | D.253 |
A
对于数列
的通项公式为
,则可得第一组为
;第二组为1,3;第三组为5,7,9,11;第四组为13,15,17,19,21,23,25,27;第五组为29,31,33,35,37,39,41,43,45,47,49,51,53,55,57,59;第六组的第一个数为61.
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130582376.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130598428.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823120130957143.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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