4 tables, so 2 players have to sit out each round. each person should partner with everyone, so there are 17 rounds. my guess is that you should play each opponent twice?
can't use a 20 team setup as the bye's dont end up at the same table every time.
first round would be
1;2 V 3;4
5;6 V 7;8
9;10 V 11;12
13;14 V 15;16
17 & 18 ON BYE