這題建表是個好方法

n <= 10000

我先建一個 1~100 的質數表

然後開始建 n! 的表

n = 2, d[n] = {2: 1}
n = 3, d[n] = {2: 1, 3: 1}
n = 4, d[n] = {2: 3, 3: 1}
n = 5, d[n] = {2: 3, 3: 1, 5:1}
.
.
.
n = 10000, d[n] = {.....}

每一個 d[n] 都是 d[n-1] + {n 的因數分解表}