12 ≤ C(21,14,4) ≤ 14

Method of Construction: dynamic programming covering

Lower Bound: Schonheim

  1  2  3  4  5  6  7  8  9 10 11 12 13 14
  1  2  3  4  5  6  7  8  9 10 11 12 15 16
  1  2  3  4  5  6  7  8  9 10 11 12 17 18
  1  2  3  4  5  6  7  8  9 10 11 12 19 20
  1  2  3  4  5  6  7  8  9 10 11 12 16 21
  2  3  5  7  8 13 14 15 16 17 18 19 20 21
  1  4  6  8  9 13 14 15 16 17 18 19 20 21
  1  3  4  5 10 13 14 15 16 17 18 19 20 21
  2  3  6  9 10 13 14 15 16 17 18 19 20 21
  1  5  7  9 11 13 14 15 16 17 18 19 20 21
  4  5  6  7 12 13 14 15 16 17 18 19 20 21
  1  2  4 11 12 13 14 15 16 17 18 19 20 21
  3  6  9 11 12 13 14 15 16 17 18 19 20 21
  7  8 10 11 12 13 14 15 16 17 18 19 20 21