C(27,13,2) = 7

Method of Construction: lexicographic greedy covering

Lower Bound: Schonheim

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