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 Subject: "pi(x) , pq(x) , (p,q both primes)" Previous Topic | Next Topic
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Pierre Charland
Member since Dec-22-05
Feb-01-08, 09:41 PM (EST)    "pi(x) , pq(x) , (p,q both primes)"

 I'm looking for info on the distribution of numbers of the form n=pq, where p and q are both primes.For number of the form n=p, where p is prime, we have the function pi(x) for the number of such n<=x. And it is know that pi(x)=x/ln(x) approximately.Is there a similar function for numbers which are the product of 2 primes? and a know approximation?Any reference or link would help.ThanksAlphaChapMtl

Pierre Charland
Member since Dec-22-05
Feb-01-08, 10:27 PM (EST)    1. "RE: pi(x) , pq(x) , (p,q both primes)"
In response to message #0

 I found that such numbers are called semiprimes.Semiprimes can have p=q.Squarefree semiprimes would have p<>q.https://mathworld.wolfram.com/Semiprime.htmlAn exact formula is given in the reference, but I was hoping for a simpler approximation formula.Further references or links still welcome. Thanks.AlphaChapMtl

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