C(28,11,2) = 10

Method of Construction: lexicographic greedy covering

Lower Bound: Schonheim

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