题目内容
某商场橱窗里用同样的乒乓球堆成若干准“正
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229483185049.jpg)
三棱锥”形的展品,其中第一堆只有一层,
就一个乒乓球;第2、3、4、…堆最底层(第
一层)分别按右图所示方式固定摆放.从第一层开始,每层的小球自然垒放在下一层之上,第n堆第n层就放一个乒乓球,以
表示第n堆的乒乓球总数,则
(答案用n表示).
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229483185049.jpg)
三棱锥”形的展品,其中第一堆只有一层,
就一个乒乓球;第2、3、4、…堆最底层(第
一层)分别按右图所示方式固定摆放.从第一层开始,每层的小球自然垒放在下一层之上,第n堆第n层就放一个乒乓球,以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823122948333271.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823122948349289.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823122948365333.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823122948396610.gif)
:![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229484271107.gif)
的规律由
,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229486301302.gif)
所以![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229486451086.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229486611142.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229484271107.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823122948333271.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823122948505858.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229486301302.gif)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229486451086.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231229486611142.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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