C(30,9,2) = 15

Method of Construction: simple construction: induced on c(31,10,3) covering

Lower Bound: Handbook of Combinatorial Designs section on coverings

  3  4 11 12 13 15 18 19 22
  5  9 13 15 17 24 26 29 30
  4  8  9 10 17 19 20 26 28
  1  4  5 14 16 19 24 25 27
  1  3  8 11 22 25 28 29 30
 10 12 14 16 18 20 27 29 30
  2  3  7  9 17 22 23 26 27
  2  3  7  9 11 14 16 26 27
  2  7  9 11 14 16 17 22 23
  6  8 13 14 15 16 21 27 28
  3  5  6 10 11 20 21 22 24
  2  5  7  8 12 18 23 24 28
  1  2  7 10 13 15 20 23 25
  2  4  6  7 19 21 23 29 30
  1  6  9 12 17 18 21 25 26