lower bound = 27

C(18,4,2) = 27

Method of Construction: mills, jcta 13 (1972) pp. 55-78.

Lower Bound: Schonheim

  1  2  3  4
  1  2  5  6
  1  7 14 16
  1  8 11 18
  1  9 13 17
  1 10 12 15
  2  7 12 17
  2  8 13 15
  2  9 11 16
  2 10 14 18
  3  4  9 10
  3  5 11 12
  3  6 15 16
  3  7 13 18
  3  8 14 17
  4  5 17 18
  4  6 13 14
  4  7 11 15
  4  8 12 16
  5  6  7  8
  5  9 14 15
  5 10 13 16
  6  9 12 18
  6 10 11 17
  7  8  9 10
 11 12 13 14
 15 16 17 18