C(18,13,2) = 3

Method of Construction: lex covering

Lower Bound: Schonheim

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