lower bound = 15

15 ≤ CC(23,7,2) ≤ 16

Method of Construction: communicated by d. todorov, using pg(2,3)

Lower Bound: Horsley, Theorem 1, r=4, d=2

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