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Learn a mathematical approach to creating more secure passcodes by understanding the probability theory behind digit repetition in PIN codes. Explore why having repeated digits in your passcode actually makes it statistically harder for attackers to guess, starting with analysis of 4-digit codes before expanding to 6-digit passcodes and general cases. Discover the counterintuitive mathematics that shows passcodes with repeated digits are more secure than those with all unique digits, supported by combinatorial calculations and probability distributions that demonstrate how this simple trick can significantly improve your digital security.