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