Really sorry for the clumsy mistake. I'm indeed testing 2*k*p +1, and p=333019 is missing in the previous message. For interest's sake I found some two smaller PRPs before this one; i.e.

(1) 2*(10^10000+36107)*333019+1 is probable prime! (verification : a = 36761) (digits:10006)

(2) 2*(10^10000+49931)*333019+1 is probable prime! (verification : a = 36761) (digits:10006)

and then lately

(3) 2*(10^100000+50617)*333019+1 is probable prime! (verification : a = 42349) (digits:100006)

Thanks to David for the verification.

Peter.

----- Original Message -----

From: Peter Lesala

To: primenumbers@yahoogroups.com ; Peter Lesala

Sent: Thursday, September 01, 2011 12:22 PM

Subject: [PrimeNumbers] A PRP of the form 2*k*p +1

Keen to find prime factors of 2^333019 - 1, I went on to test 2*k*p + 1 for k = 10^100000. The test gives

2*(10^100000 + 50617) + 1 as a probable prime of 100006 digits; using Primeform.

Peter.

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