lower bound = 9

C(7,5,4) = 9

Method of Construction: lex covering

Lower Bound: Schonheim

  1  2  3  4  5
  1  2  3  6  7
  1  4  5  6  7
  2  3  4  5  6
  2  3  4  5  7
  1  2  4  6  7
  1  2  5  6  7
  1  3  4  6  7
  1  3  5  6  7