PRP in base 11 and 13

For (85^n-83^n)/2, I found hitherto:
(85^3-83^3)/2
(85^11-83^11)/2
(85^23-83^23)/2
(85^29-83^29)/2
(85^71-83^71)/2
(85^12763-83^12763)/2
(85^17387-83^17387)/2
(85^28751-83^28751)/2

To be completed...