Yes sure, the numbers are going infinite, but the indicator function on the set ai has periodic behaviour. That is what I am aiming at.
To illustrate take the following two simple sets to begin with:
Let ai = { 7, 4, 7, 4, 7, 12, 3, 12 }
and bj = { 12, 6, 11, 6, 12, 18, 5, 18 }...