21 ≤ C(21,9,3) ≤ 24
Method of Construction: simple construction: induced on c(22,10,4) covering
Lower Bound: Schonheim
2 3 4 5 8 10 17 18 20
2 3 4 6 9 10 16 18 19
2 3 5 6 7 8 9 15 21
1 2 3 7 11 12 13 14 18
2 4 5 6 7 14 19 20 21
1 2 4 9 11 12 13 15 20
1 2 5 10 11 12 13 16 21
1 2 6 8 11 12 13 17 19
2 7 9 10 14 15 16 17 19
2 8 14 15 16 17 18 20 21
3 4 7 8 9 13 16 17 21
1 3 4 8 11 12 14 15 19
3 5 7 10 13 15 17 19 20
1 3 5 9 11 12 14 16 20
1 3 6 10 11 12 14 17 21
3 6 13 15 16 18 19 20 21
1 4 5 6 11 12 15 16 17
4 5 9 13 14 17 18 19 21
4 6 7 8 10 13 14 16 20
1 4 7 10 11 12 15 18 21
5 6 8 9 10 13 14 15 18
1 5 7 8 11 12 16 18 19
1 6 7 9 11 12 17 18 20
1 8 9 10 11 12 19 20 21