Found with PFGW Version 3.6.0

1284^3899-3899^1284 is 2-PRP! (5.6847s+0.0032s)
1284^3899-3899^1284 is 3-PRP! (6.0640s+0.0020s)
1284^3899-3899^1284 is 5-PRP! (5.7711s+0.0024s)
1284^3899-3899^1284 is 7-PRP! (5.7144s+0.0018s)
1284^3899-3899^1284 is 11-PRP! (5.6946s+0.0018s)

Primality testing 1284^3899-3899^1284 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 5
Running N+1 test using discriminant 11, base 2+sqrt(11)
Calling N-1 BLS with factored part 0.02% and helper 0.02% (0.09% proof)
1284^3899-3899^1284 is Fermat and Lucas PRP! (27.4640s+0.0018s)

To be completed...