20210915, 11:19  #265  
Sep 2002
Database er0rr
5×7×109 Posts 
Quote:
https://primes.utm.edu/primes/page.php?id=132715 is a palindrome. Congrats Serge and Ryan. UTM's Prime Pages parser calculated the decimal digits as 1234568 Last fiddled with by paulunderwood on 20210915 at 11:45 

20210915, 16:06  #266  
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2^{6}×149 Posts 
Quote:
All palindromes of even length (except 11) are composite! Hint: they are divisible by 11 

20210915, 18:17  #267  
Jun 2015
Vallejo, CA/.
1755_{8} Posts 
Quote:
I have to see it to believe it! 

20210915, 21:52  #268 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2540_{16} Posts 
When I was already way into sieving, I thought that I should have picked 1234321 decimal digits length
But it turned out good. With 1234567 digits' dataset the hit came, statistically speaking, very! early. So it was lucky. 
20210921, 00:39  #269 
Sep 2002
Database er0rr
5·7·109 Posts 
The prof has been busy. He fixed the palindrome length and puzzlepeter's arithmetic progression, which comes second on table two of https://primes.utm.edu/top20/page.php?id=14.
Hint: An AP9 could be quite easy to find to make it to the top of table two. For the AP8, I wrote my own GWNUM code which was 15% faster, I think mainly by dropping repetitive evaluations of the primorial coefficient. I'd willing to share it with any interested parties. Last fiddled with by paulunderwood on 20210921 at 00:41 
20210921, 01:30  #270 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
10010101000000_{2} Posts 
Good! Excellent!
Even Kamadasan wrote to him and cc:'d me (as if I could help ). But it is fixed now, cool beans. 
20210922, 10:07  #271  
Dec 2011
After milion nines:)
1468_{10} Posts 
Quote:
So if it is not secret how many candidates was tested before prime appear? 

20210922, 12:51  #272 
Jun 2012
Boulder, CO
313 Posts 

20210922, 20:54  #273 
Dec 2011
After milion nines:)
2^{2}×367 Posts 

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