lower bound = 20

20 ≤ CC(13,6,3) ≤ 21

Method of Construction: random greedy covering

Lower Bound: Schonheim

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