题目：

题解：

class Solution {
    public int countArrangement(int n) {
        int[] f = new int[1 << n];
        f[0] = 1;
        for (int mask = 1; mask < (1 << n); mask++) {
            int num = Integer.bitCount(mask);
            for (int i = 0; i < n; i++) {
                if ((mask & (1 << i)) != 0 && ((num % (i + 1)) == 0 || (i + 1) % num == 0)) {
                    f[mask] += f[mask ^ (1 << i)];
                }
            }
        }
        return f[(1 << n) - 1];
    }
}