The reason this PRP s form is so strange is that it is based on "mock-rational numbers" -- those that exhibit patterns in their digits. Its decimal expansion consists of many repeating single digits separated by “random” strings.

Resuming input file MOCK3.txt at line 1
[N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 2
Running N+1 test using discriminant 7, base 1+sqrt(7)
2222222222222222....0000000000000421 is Fermat and Lucas PRP!

To be completed...