MathForces: Math Olympiads

# Factorial Factor

Author: mathforces
Problem has been solved: 59 times

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Lin randomly selected a factor of $21! = 1 \cdot 2 \cdot 3 \cdot ... \cdot 21$. Let $\frac{n}{m}$ be an irreducible fraction - the probability that the divisor is odd. What is $( |n| + 1)^2m^2$ equal to?

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