lower bound = 21

21 ≤ CC(24,6,2) ≤ 22

Method of Construction: found by a hill-climbing program

Lower Bound: Horsley, Theorem 1, r=5, d=2

  6 12 13 18 19 23
  2  5  7  9 15 18
  5 14 15 20 23 24
  1  2  3 10 12 24
  1  4  5 10 17 22
  2  6 11 17 22 23
  3  8 15 17 19 22
  4 10 14 17 18 22
  2  4  5  8 13 20
  1  7  8 10 21 23
  3  4 11 18 20 21
  3  4  5  9 16 23
  8  9 11 12 14 20
  9 13 17 21 22 24
  4  5  6 12 15 21
  7 12 16 17 20 22
  1  3  6  7 13 14
  4  5  7 11 19 24
  1  6  9 10 19 20
  1  6  8 16 18 24
  2 14 16 19 21 24
  1 10 11 13 15 16