Primality testing 1240^19737-19737^1240 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 3
Running N-1 test using base 7
Running N+1 test using discriminant 13, base 2+sqrt(13)
Calling N+1 BLS with factored part 0.02% and helper 0.01% (0.06% proof)
1240^19737-19737^1240 is Fermat and Lucas PRP! (185.1497s+0.0013s)

Sieved with xyyxsieve

To be completed...