PRP in base 79 and 83

For (57^n-1)/56, I found hitherto:
(57^3-1)/56
(57^17-1)/56
(57^109-1)/56
(57^151-1)/56
(57^211-1)/56
(57^661-1)/56
(57^16963-1)/56
(57^22037-1)/56

To be completed...