[gmo]

Maybe I can give a helpful hint. For the interdivision games, rather than treating each subleague as 5 divisions of 4 teams, split up each division and treat it as though there are 10 "half-divisions" of 2 teams.

Then you have an even number of "half-divisions" to allow for everybody in the league to have an interdivision matchup at the same time. Just make sure to exclude the divisional matchups from getting into those "half-divisions" matchups.

Here is an example of splitting each division into half-divisions "A" and "B"...

2A 1A    3A 1B    4A 2B    5A 3B    5B 4B
1A 3A    4A 2A    5A 1B    5B 2B    4B 3B
4A 1A    5A 3A    5B 2A    4B 1B    3B 2B
1A 5A    5B 4A    4B 3A    3B 2A    2B 1B
5B 1A    4B 5A    3B 4A    2B 3A    1B 2A
1A 4B    3B 5B    2B 5A    1B 4A    2A 3A
3B 1A    2B 4B    1B 5B    2A 5A    3A 4A
1A 2B    1B 3B    2A 4B    3A 5B    4A 5A

Each half-division matches up there once against each other half-division outside its division. (Maybe double-check my work to make sure)

The upper-left pod of "2A 1A" corresponds to four games since 1A encompasses teams 1 & 2 and 2A encompasses teams 5 & 6...

5 v 1    6 v 2
6 v 1    5 v 2