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Re:利用数学

Posted by suikay at 2009-03-11 12:53:34 on Problem 1604
In Reply To:利用数学 Posted by:8013 at 2004-03-20 11:32:39

> 我记得没错的话，是求n!的最后一位非零的吧？记为f(n)
> 根据式子
>                     n-1
>    (5n)! =  (10^n)n! ∏(5i+1)(5i+2)(5i+3)(5i+4)/2
>                      i=0
> 
> 可证明  f(5n)≡(2^n)f(n) (mod10)就可以了
还是数学好用阿～

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