20220522, 09:27  #507 
"Norbert"
Jul 2014
Budapest
2^{2}×31 Posts 
Another new PRP:
37535^37674+37674^37535, 172338 digits. 
20220527, 05:47  #508 
Nov 2019
10101_{2} Posts 
My 'Leyland1M' project found this PRP:
211185^54364+54364^211185 is Fermat and Lucas PRP! 1000027 digits, index: 21589915517 (if my program is correct). 
20220527, 10:41  #509 
Sep 2010
Weston, Ontario
2×7×17 Posts 
Well done! The Leylandnumber index is correct. I have a dictionary of Leyland (x,y) pairs from (999999,10) to (1000999,10), sorted by magnitude and preceded by its Leylandnumber index (21588818851 to 21628375832), so I can just look it up.

20220531, 18:06  #510  
Sep 2010
Weston, Ontario
2·7·17 Posts 
Quote:
I have just now changed this line to: 715 38951950 30008 (8656,2929) Anatoly Selevich Dec 2007 P I don't know why I hadn't thought of this before. The Internet Archive Wayback Machine has a Jan 2008 snapshot that definitively dates the PRP discovery. 

20220619, 18:30  #511 
"Norbert"
Jul 2014
Budapest
2^{2}·31 Posts 
Another new PRP:
33^129128+129128^33, 196083 digits. 
20220624, 15:36  #512 
"Norbert"
Jul 2014
Budapest
7C_{16} Posts 
Another new PRP:
37803^37916+37916^37803, 173562 digits. 
20220626, 17:22  #513 
Random Account
Aug 2009
Not U. + S.A.
2538_{10} Posts 

20220626, 17:31  #514 
Sep 2002
Database er0rr
118F_{16} Posts 

20220628, 13:40  #515  
Random Account
Aug 2009
Not U. + S.A.
2×3^{3}×47 Posts 
Quote:
What are these calculation being done with? 

20220628, 14:27  #517 
"Mark"
Apr 2003
Between here and the
3×23×101 Posts 
He has a special build of xyyxsieve because the way he is testing ranges is based upon decimal length of the candidates. The "out of the box" xyyxsieve is more efficient with a relatively square workspace, i.e. the range of x and y are similar in size. At one time I was working on changing xyyxsieve to be provide the "best of both worlds", but I couldn't get it to work and gave up. I might return to it someday.
The biggest challenge with xyyxsieve is that it is most efficient to sieve a very large search space once than to break that up into smaller chunks. But with a very large search space one needs a lot of memory. 
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