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我是用DP做的。dp[i][j]代表前i个数最大公约数是j的种数,这里的话最大公约数状态是m的因子,所以要离散化一下。

Posted by yygy at 2012-11-23 01:12:50 on Problem 1091
dp[0][m]=1

dp[i][j]=sum{dp[i-1][k]*Eul(m/(k/j),k/j)} where k%j==0;

Eul(n,t)为n和t互质的个数。

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