C(28,10,2) = 11

Method of Construction: lexicographic greedy covering

Lower Bound: Schonheim

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