C(28,13,2) = 7

Method of Construction: simple construction: added element to c(v,k-1,t) covering

Lower Bound: Schonheim

  8  9 10 11 12 17 18 19 20 25 26 27 28
  1  2  3  4  8 13 14 15 16 17 18 19 20
  8 13 14 15 16 21 22 23 24 25 26 27 28
  1  2  3  4  5  6  7  8 20 25 26 27 28
  2  5  6  7  8 17 18 19 20 21 22 23 24
  5  6  7  8  9 10 11 12 13 14 15 16 28
  1  2  3  4  9 10 11 12 14 21 22 23 24