C(15,7,2) <=7

Method of construction: lex covering

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