lower bound = 20

20 ≤ CC(23,6,2) ≤ 21

Method of Construction: found by a hill-climbing program

Lower Bound: Schonheim

 10 11 13 17 19 20
  1  4  9 11 12 14
  5  7 15 17 20 21
  1  5  6  8 13 22
  6  7 11 14 16 21
  6  9 13 15 16 23
  4  5 12 13 16 18
  1  3  4  7 12 15
  1  2 10 16 19 23
  3  8 16 17 20 22
  7 14 17 18 20 23
  2  8 11 15 18 22
  1  9 17 18 20 21
  2  3  5  9 11 23
  5 10 14 19 21 22
  3  4  6 10 18 19
  2  3  7 13 14 21
  8 10 12 14 15 19
  7  8  9 10 19 22
  4  8 12 21 22 23
  2  4  6 12 17 20