20 ≤ C(28,16,4) ≤ 24

Method of Construction: simple construction: multiple of smaller covering

Lower Bound: Schonheim

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