lower bound = 35

C(20,4,2) = 35

Method of Construction: random greedy covering

Lower Bound: Schonheim

  3  6 17 20
 11 15 16 19
  5  7 14 15
  2  7  9 20
  1  9 13 15
  3  7 11 13
 12 13 18 19
  4  5  6  8
  1  5 10 11
  1  6  7 16
  4 11 18 20
  8 12 15 20
  4 13 14 17
  1  2  4 19
  6  9 10 12
  3  8  9 16
  7  8 17 18
  2 10 14 16
  1  3 14 18
  2 11 12 17
  2  6 15 18
  3  4 10 15
  5  9 17 19
  5 13 16 20
  8 11 14 19
  2  8 10 13
  7 10 19 20
  4  7 12 16
  2  3  5 12
  1 12 14 20
 10 16 17 18
  6  9 11 14
  1  8 15 17
  3  6 13 19
  4  5  9 18