Best way to map two sets of data

a newbie here. So I have two sets of data that I'm creating test cases for to map them in different ways in c++. Both the sets of data go from 0 to 511. For example here is one of my cases:

This pattern maps channels with an offset. The user specifies the channel to begin mapping to and the program starts mapping channel 0 and onwards. Once the output reaches 511, the program loops back to the beginning of the output channels.

Ex.

CH#

0               200

...     -->     ...

311             511

312             0

...     -->     ...

511             199

This is for a functionality I'm testing. What are some good/unique mappings you guys can think of?

Thanks in advance!