# Combinatoric system which using in bookies "S3" system

I am interested what type of combinatorics is using for following bookmakers system called "S3":

1. We have N={1..8} events
2. We build express pairs C=8 like

[(1, 2, 4), (1, 3, 6), (1, 6, 8), (2, 3, 5), (2, 5, 8), (3, 7, 8), (4, 5, 7), (4, 6, 7)]

Each event repeats 3-times: 1 => (1, 2, 4), (1, 3, 6), (1, 6, 8)..

It's not permutation, combination... Please advice what is it?

I want as example generate in similar way 4 from 10 if this possible. After I'd like to predict the optimal way for building the `pairs'