An example? Where A = a horse, B = a different horse etc. :D
Race 1: A,B
Race 2: C,D,E
Race 3: F
These are the bets in a permed patent:
Singles: A,B,C,D,E,F
Doubles: AC,AD,AE,AF,BC,BD,BE,BF,CF,DF,EF
Trebbes: ACF,ADF,AEF,BCF,BDF,BEF
I think that's right...