18 ≤ C(55,15,2) ≤ 19

Created by: LJCR

Method of Construction: Multiple of (11,3,2) covering

Lower Bound: Horsley, Theorem 1, r=4, d=2

  1  2  6 12 13 17 23 24 28 34 35 39 45 46 50
  1  3 11 12 14 22 23 25 33 34 36 44 45 47 55
  1  4  9 12 15 20 23 26 31 34 37 42 45 48 53
  1  5  8 12 16 19 23 27 30 34 38 41 45 49 52
  1  7 10 12 18 21 23 29 32 34 40 43 45 51 54
  2  3  8 13 14 19 24 25 30 35 36 41 46 47 52
  2  4 10 13 15 21 24 26 32 35 37 43 46 48 54
  2  5 11 13 16 22 24 27 33 35 38 44 46 49 55
  2  7  9 13 18 20 24 29 31 35 40 42 46 51 53
  3  4 11 14 15 22 25 26 33 36 37 44 47 48 55
  3  5  7 14 16 18 25 27 29 36 38 40 47 49 51
  3  6 10 14 17 21 25 28 32 36 39 43 47 50 54
  3  9 11 14 20 22 25 31 33 36 42 44 47 53 55
  4  5  6 15 16 17 26 27 28 37 38 39 48 49 50
  4  7  8 15 18 19 26 29 30 37 40 41 48 51 52
  5  9 10 16 20 21 27 31 32 38 42 43 49 53 54
  6  7 11 17 18 22 28 29 33 39 40 44 50 51 55
  6  8  9 17 19 20 28 30 31 39 41 42 50 52 53
  8 10 11 19 21 22 30 32 33 41 43 44 52 54 55