Hey, I am trying to figure out an algorithm to find the largest HCN lower than n(<10^18). I have developed an algorithm that solve my problem and it works fast, but i don't know an upperbound of the complexity of this algorithm. A necessary condition for k to be a HCN is that all his primes factors are consecutive starting from 2, and the exponents of each prime are in a non-increasing sequence. (Both conditions are easy to demonstrate) I am doing backtracking using this condition, as I say earlier the program run fast but I don't know why, could you explain to my why does it happen or another approach of this problem?? Thks