If you have a class of 90 students:
Year 1, you want to split them into 2 equal groups
Year 2, 3 equal groups (or near equal)
Year 3, 4 groups
Year 4, 5 groups
Year 5, 6 groups
****The students should not be in the same group as someone they have already been with (as much as possible)
What formula can I use?