C(21,13,3) = 9

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
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  1  2  3 12 13 14 15 16 17 18 19 20 21
  4  5  6 12 13 14 15 16 17 18 19 20 21
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