C(15,5,2) = 13

Method of Construction: random greedy covering

Lower Bound: Horsley, Theorem 1, r=4, d=2

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