Found with PFGW Version 3.6.0

91^18886-90 is 2-PRP! (25.0912s+0.0025s)
91^18886-90 is 3-PRP! (21.3085s+0.0024s)
91^18886-90 is 5-PRP! (21.5023s+0.0028s)
91^18886-90 is 7-PRP! (22.0395s+0.0025s)
91^18886-90 is 11-PRP! (22.0248s+0.0024s)

Primality testing 91^18886-90 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 3
Running N+1 test using discriminant 7, base 6+sqrt(7)
Calling N-1 BLS with factored part 0.07% and helper 0.00% (0.21% proof)
91^18886-90 is Fermat and Lucas PRP! (144.7629s+0.0024s)

To be completed...