lower bound = 19

C(15,4,2) = 19

Method of Construction: random greedy covering

Lower Bound: Schonheim

  2  3  4  5
  9 10 11 15
  3  8 12 13
  1  3  7 11
  2  7 12 14
  3  6 14 15
  1  6  8  9
  5  7  8 10
  4  7 13 15
  1  5 13 14
  1  4 10 12
  2  6 10 13
  5  6 11 12
  4  8 11 14
  1  2  8 15
  4  6  7  9
  5  9 12 15
  2  9 11 13
  3  9 10 14