Theorem 10: Prime Counting Function and Loglog x

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Discussion Overview

The discussion revolves around Theorem 10 from Hardy's book on number theory, specifically the prime counting function pi[x] and its relationship to loglog x. Participants are seeking clarification on the theorem's proof and related concepts, including the implications of Bertrand's postulate.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant expresses confusion regarding the theorem stating that pi[x] is greater than or equal to loglog x and requests help with understanding the arguments presented in the book.
  • Another participant questions whether others understand the derivation of the bound p_{n} < 2^{2^n}, suggesting it is a crucial step in the proof.
  • A third participant brings up Bertrand's postulate, indicating a potential connection to the discussion.
  • A later reply asserts that the bound on p_n is weaker than what Bertrand's postulate provides but notes that it is simpler to prove, referencing Euclid's proof of the infinitude of primes as a basis for this adaptation.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the understanding of the theorem or the derivation of the bounds discussed. Multiple competing views and interpretations remain present.

Contextual Notes

Some participants express uncertainty regarding specific steps in the proof and the implications of the theorem, indicating that further clarification on definitions and assumptions may be necessary.

AlbertEinstein
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I am going through Hardy's book on number theory.The following theorem I do not understand.

theorem 10: pi[x] >= loglog x
where pi[x] is the prime counting function
and >= stands for greater than or equal to

The arguments written in the book are very compact.please help .
 
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Do you follow any of it?

Do you understand how they derived [tex]p_{n}<2^{2^n}[/tex] ?

this is an important step. The rest just follows from pi(x) being increasing, and also [tex]\pi(p_n)=n[/tex] which they use but don't explicitly mention.
 
Bertrand's postulate?
 
Nope! the bound of p_n above is much weaker than Bertrand's will give you. It's correspondingly simpler to prove though, it follows from a slight adaptation of Euclid's proof there are infinitely many primes (in case anyone who hasn't seen it wants to give it a stab)
 

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