Quote:
Originally Posted by davar55
Any progress on this curious number a(20)?
What's the likelihood that a 750k1M digit candidate will be a PRP?
Or that all of the candidates in that range will be composite?

#20 at 833K digits atm, no PRP.
Quick (and very rough) approximation that a random pick
with n decimal digits is prime: 1 : 2.3n
Chance to find none between 750K and 1M is around 90%.