channel 0 is ouptuts 0,1,2 channel 1 is outputs 3,4,5 channel 2 is outputs 6,7,8 channel 3 is outputs 9,10,11 channel 4 is outputs 12,13,14
There's a very simple formula in there, screaming to be let out.
Increments may look cool, but they have a nasty side-effect, which you'll find when you come to try the code out.
Best to anticipate it though.
Yes, you're right, I do like tables.
They allow a degree of flexibility if you decide to change your wiring that arithmetic may not.
And I really would not worry about speed where these values are concerned.