C(9,6,3) <=7

Method of construction: dynamic programming covering

 1  2  3  4  5  6
 1  2  3  4  5  7
 1  2  3  4  5  8
 1  2  3  4  5  9
 1  2  6  7  8  9
 3  4  6  7  8  9
 1  5  6  7  8  9