C(31,11,2) = 12

Method of Construction: lexicographic greedy covering

Lower Bound: Bounds for fixed number of blocks

  1  2  3  4  5  6  7  8  9 10 11
  1 12 13 14 15 16 17 18 19 20 21
  1 22 23 24 25 26 27 28 29 30 31
  2  3  4  5 12 13 14 15 22 23 24
  2  3  4  5 16 17 18 19 25 26 27
  6  7  8  9 12 13 14 15 25 26 27
  6  7  8  9 16 17 18 19 22 23 24
  2  3  4  5  6 20 21 28 29 30 31
 10 11 12 13 14 15 16 28 29 30 31
  7 10 11 20 21 22 23 24 25 26 27
  7  8  9 10 17 18 19 28 29 30 31
  1  2  3  8  9 11 17 18 19 20 21