I have seen a problem like : given an array of length n, there is an edge between two elements a[i] and a[j] if lcm(a[i], a[j]) >= some number, or gcd(a[i], a[j]) != 1. Help me find such problems. If there is any tip like how to approach these problems, because I can't store the adjacency list from the array because it would be n * n.