result to store the number of valid pairs.gcdMap to store the count of numbers by their GCD with k.nums:
a. Calculate the GCD of the current number and k.
b. For each previously encountered GCD in gcdMap, check if the product of the current GCD and the previous GCD is divisible by k.
c. If divisible, increment result by the count of the previous GCD in gcdMap.
d. Update gcdMap with the current GCD count.result.