C(13,9,4) = 10

Method of Construction: dynamic programming covering

Lower Bound: Theorem 4, Todorov, JCTA 1985

  1  2  3  4  5  6  7  8  9
  1  2  3  4  5  6  7 10 11
  1  2  3  4  5  6  7 12 13
  1  2  3  8  9 10 11 12 13
  1  4  5  8  9 10 11 12 13
  1  6  7  8  9 10 11 12 13
  2  4  6  8  9 10 11 12 13
  2  5  7  8  9 10 11 12 13
  3  4  7  8  9 10 11 12 13
  3  5  6  8  9 10 11 12 13