C(19,4,2) = 31

Method of Construction: simple construction: induced on c(20,5,3) covering

Lower Bound: Mills

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