lower bound = 18

C(18,5,2) = 18

Method of Construction: cyclic covering found by a search program

Lower Bound: Schonheim

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