lower bound = 59

C(26,4,2) = 59

Method of Construction: simple construction: combined (25,4,2) and (25,3,1)-coverings

Lower Bound: Schonheim

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