Generalized repunit prime (base 203).
For base 201, I found R271, R353.
For base 202, I found R37, R829.
For base 203, I found R3, R7, R31, R9587.
For base 204, I found R5, R359.
For base 205, I found R19, R61, R6427, R8147.
For base 206, I found R3, R7.

To be completed...