mersenneforum.org 10^n+7: four PRPs
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2021-06-08, 07:20   #1
Alfred

May 2013
Germany

5·17 Posts
10^n+7: four PRPs

I've found four probable primes in the range 200001 <= n <= 500000:

Code:
n = 221628, 350071, 371696, 487291.
IMO any other 10^n+7 is composite.

The attached file should "prove" this assertion.
Attached Files
 10w7.PRPsearch.Proof.txt.7z (1.16 MB, 15 views)

2021-06-08, 09:33   #2
axn

Jun 2003

13·17·23 Posts

Quote:
 Originally Posted by Alfred IMO any other 10^n+7 is composite.
Do you mean "any other" in the specified range? Or n=[1..oo]?

 2021-06-08, 11:23 #3 Alfred     May 2013 Germany 5·17 Posts Any other in the specified range is meant.
2021-06-08, 11:48   #4
Dr Sardonicus

Feb 2017
Nowhere

4,673 Posts

Quote:
 Originally Posted by axn Do you mean "any other" in the specified range? Or n=[1..oo]?
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.

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