C(18,12,3) = 6

Method of Construction: simple construction: multiple of smaller covering

Lower Bound: Schonheim

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