lower bound = 28

28 ≤ CC(13,7,4) ≤ 30

Method of Construction: nurmela and ostergard simulated annealing cover

Lower Bound: Schonheim

  1  2  5  6  7  8  9
  1  3  4  5  6  8 10
  2  3  6  7  8  9 10
  2  3  4  5  8  9 11
  1  3  5  7  8 10 11
  1  2  4  8  9 10 11
  1  2  3  5  7 10 12
  1  3  4  5  9 10 12
  1  2  4  5  6 11 12
  1  3  6  7  9 11 12
  2  6  7  8  9 11 12
  4  6  7  8  9 11 12
  2  3  4  6 10 11 12
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  3  4  5  6  7  9 13
  1  2  3  5  6 10 13
  1  4  6  7  9 10 13
  1  2  3  4  7 11 13
  2  4  7  8  9 11 13
  2  4  5  7 10 11 13
  1  3  5  9 10 11 13
  1  4  5  7  8 12 13
  2  4  6  7  8 12 13
  1  2  3  8  9 12 13
  3  4  7  8 10 12 13
  2  5  8  9 10 12 13
  3  5  6  8 11 12 13
  2  4  6  9 11 12 13
  6  7  8  9 11 12 13
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