20210608, 07:20  #1 
May 2013
Germany
3×29 Posts 
10^n+7: four PRPs
I've found four probable primes in the range 200001 <= n <= 500000:
Code:
n = 221628, 350071, 371696, 487291. The attached file should "prove" this assertion. 
20210608, 09:33  #2 
Jun 2003
3×17×101 Posts 

20210608, 11:23  #3 
May 2013
Germany
3·29 Posts 
Any other in the specified range is meant.

20210608, 11:48  #4 
Feb 2017
Nowhere
3^{2}·557 Posts 
I see the OP has answered graciously.
I would have been tempted to answer "Yes." I point out If the attached file was supposed to prove that 10^n + 7 is composite for all other n, it would have been big news if it actually did that. (Especially since 10^n + 7 is prime for n = 1, 2, 4, 8, and 9). A proof that 10^n + 7 is composite for all n greater than 5000000 would also be big news. 
20210922, 09:15  #5  
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
22547_{8} Posts 
Quote:
Send those findings to him... and to OEIS: https://oeis.org/A088274 

20210927, 01:36  #6 
Romulan Interpreter
"name field"
Jun 2011
Thailand
9801_{10} Posts 
Buuuu! Are you a mersenne prime hunter or not?
(hint: 17, 107) Last fiddled with by LaurV on 20210927 at 01:42 
20210927, 01:41  #7 
Romulan Interpreter
"name field"
Jun 2011
Thailand
10011001001001_{2} Posts 

20210927, 03:23  #8  
Feb 2017
Nowhere
3^{2}×557 Posts 
Quote:
Of course, a proof that there are infinitely many such primes would also represent an enormous conceptual advance, and would be much more satisfying all around. 

20210927, 03:34  #9 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
5^{2}·383 Posts 
Kamada's updated his site, I see.
I updated OEIS. 
20210927, 03:41  #10  
"99(4^34019)99 palind"
Nov 2016
(P^81993)SZ base 36
2·1,531 Posts 
Quote:


20210927, 05:55  #11 
May 2013
Germany
1010111_{2} Posts 

Thread Tools  
Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Near and quasirepunit PRPs  Batalov  And now for something completely different  10  20190912 13:31 
Very (large) PRPs?  PawnProver44  Information & Answers  95  20160520 18:24 
PRPs not prime  schickel  FactorDB  1  20150803 02:50 
Proven PRPs?  Random Poster  FactorDB  0  20120724 10:53 
PRPs that are composites  gd_barnes  Conjectures 'R Us  57  20110912 12:31 