C(13,7,2) <=6

Method of construction: lex covering

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