Twenty golfers wish to play in foursomes for 5 days. Is it possible for each golfer to play no more than once with any other golfer? The answer is yes, and the following table gives a solution.
Mon
ABCD
EFGH
IJKL
MNOP
QRST
Tue
AEIM
BJOQ
CHNT
DGLS
FKPR
Wed
AGKO
BIPT
CFMS
DHJR
ELNQ
Thu
AHLP
BKNS
CEOR
DFIQ
GJMT
Fri
AFJN
BLMR
CGPQ
DEKT
HIOS
Event organizers for bowling, golf, bridge, or tennis frequently tackle problems of this sort, unaware of the problem complexity. In general, it is an unsolved
problem. A table of known results is maintained by Harvey.