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Joseph O'Rourke
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Distribution of the number of prime factors

Count the number of prime factors of a number $n$ to include multiplicity, so that $$n=24=2^3 \cdot 3 = 2 \cdot 2 \cdot 2 \cdot 3$$ has $4$ prime factors, and $$n = 6500 = 2^2 \cdot 5^3 \cdot 13 = 2 \cdot 2 \cdot 5 \cdot 5 \cdot 5 \cdot 13 $$ has $6$ prime factors.

The distribution is quite regular. Here it is for $n \le n_\max$, $n_\max=10^7$:


          [![DistPrimeFacts][1]][1]
          About a quarter of $n \le 10^7$ have $3$ prime factors.

Q. What is this distribution explicitly? Where is its peak, for $n \le n_\max$?

Joseph O'Rourke
  • 150.9k
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  • 358
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