20100903, 13:41  #23 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
10266_{8} Posts 
While it's subjective, I'd say these are much easier to spot as composite than 91, since one is a multiple of 11, and the other is a square. 91, on the other hand, is 7 times a prime greater than 10 that doesn't produce a clearlyvisible way to identify it (e.g. with 11 times a single digit both digits are the same, and with 3 you can see that the digits add to a multiple of 3, but to see 91=7*13 I'd have to break it as 70+21 and then see that 21 is a multiple of 7).
Last fiddled with by MiniGeek on 20100903 at 13:44 
20100903, 14:13  #24  
"Bob Silverman"
Nov 2003
North of Boston
2^{3}×3×311 Posts 
Quote:
are participating, I do have something material to add here. Look up the paper by Selfridge et.al. entitled "Primes at a Glance" 

20100903, 17:31  #25  
"Lucan"
Dec 2006
England
2×3×13×83 Posts 
Quote:
participating, will he agree that the first uninteresting number is greater than 91? David 

20100903, 17:55  #26 
Aug 2006
3·1,993 Posts 
Please be kind.
R. D. Silverman's recommendation is excellent. I might also mention the AgohErdősGranville followup paper "Primes at a (somewhat lengthy) glance", probably one of the last papers Erdős wrote. 
20100904, 00:01  #27 
"Lucan"
Dec 2006
England
6474_{10} Posts 
Hmm.
I thought quoting the great man verbatim was cutting but appropriate and witty. If he is that thinskinned, he should moderate his own tone. I was merely attempting to console the targets of his original jibe. I'm sure his and your recommendations are valuable, enjoyable and maybe even readable David 
20100904, 02:10  #28  
May 2010
Prime hunting commission.
2^{4}·3·5·7 Posts 
Quote:
Quote:
Last fiddled with by 3.14159 on 20100904 at 02:15 

20100904, 04:21  #29 
Aug 2006
3×1,993 Posts 

20100904, 04:53  #30  
May 2010
Prime hunting commission.
2^{4}×3×5×7 Posts 
Quote:
Last fiddled with by 3.14159 on 20100904 at 04:54 

20100904, 13:21  #31 
"Lucan"
Dec 2006
England
14512_{8} Posts 

20100904, 13:26  #32  
"Lucan"
Dec 2006
England
2×3×13×83 Posts 
Quote:
I believe the current parlance is "head up one's arse". David 

20100904, 14:12  #33  
May 2010
Prime hunting commission.
2^{4}·3·5·7 Posts 
Quote:


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