lower bound = 12

C(12,4,2) = 12

Method of Construction: cyclic covering found by a search program

Lower Bound: Schonheim

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