I want to generate a random string consists of lower- upper-case letters and digits. In addition, the length of this string is variable ranging from 4 to 6. For example, the first word is 3rT6, the second is DGJeH, third is LLG5us.
What is the permutations formula to calculate it.
Is it correct to calculate it using the following:
W is the number of characters and n is the number of the character set,