C(21,14,3) = 7

Method of Construction: dynamic programming covering

Lower Bound: Handbook of Combinatorial Designs section on coverings

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