13 ≤ C(23,12,3) ≤ 14

Method of Construction: simple construction: deleted element from c(v+1,k,t) covering

Lower Bound: Horsley-Singh, Theorem 6, s=1

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