P-1, like any other GCD-based factorisation method, will yield a composite result in the event that there are two (or more) prime factors within its search space. It seems unlikely that this would happen in practice because unless both were > ~ 64 bits, one of them would most likely have been found earlier during TF. However given that some factors found have been > 130 bits, then the possibility is there.
I was wondering if returned factors are checked for primality. Regards Daran G. _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
