Leetcode 2572. Count the Number of Square-Free Subsets

Count the number of non-empty subsets whose product is square-free (no prime squared divides it) modulo 1e9+7. With nums[i] ≤ 30 and n ≤ 1000, the core challenge is avoiding repeated prime factors across subset elements—typically solved by counting frequencies and using DP over prime-factor bitmasks (treating 1s separately).