Sieved to 10^9, 3-PRP in PFGW

Primality testing 855^18538-18538 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 5
Running N+1 test using discriminant 19, base 1+sqrt(19)
Calling N-1 BLS with factored part 0.02% and helper 0.01% (0.08% proof)
855^18538-18538 is Fermat and Lucas PRP!

To be completed...