(2n-1)/2
My answer is ...
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Explanation.....
-Commentate-
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11/11/2010 postreply
10:01:53
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回複:Explanation.....
-wushuihe-
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11/11/2010 postreply
17:50:48
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how about n=1?....n is right
-jinjing-
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11/11/2010 postreply
16:03:20