20061019, 00:43  #1 
Aug 2004
New Zealand
3×73 Posts 
Exercise 1.23 in Crandall & Pomerance
I know this isn't a factoring question, but you're the ones I like
to talking to. Excercise 1.23 in Crandall & Pomerance requires one to show sum_{p <= x} (ln(p) / p) = ln(x) + O(1) and then show that this implies pi(x) = O(x/ln x). I have done the first part, but I can't manage the second. I've been trying various bounds on the terms of the sum, so that I can write something like ln(x) + O(1) >= A * sum_{p <= x} 1 = A * pi(x) but nothing I have tried has given me a tight enough bound. Ideas? 
20061019, 14:00  #2  
Nov 2003
2×3×11×113 Posts 
Quote:
Now, do a different estimate of the left hand side using a Stieltje's integral with respect to pi(x). i.e. int from 2 to x of log(y)/y d[pi(y)] Integrate by parts. 

20061023, 21:08  #3 
Aug 2004
New Zealand
3·73 Posts 
Thanks Bob. I still haven't got it sorted, although I now understand a lot more about the Stieltjes integral than I did before. I'll spend some more time on it, and may ask you privately if I still can't get it sorted in a few days.
Cheers, Sean. 
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