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== Football pools problem ==
A particular case is the '''football pools problem''', based on [[football pool]] betting, where the aim is to replicatecome up with a betbetting onsystem over ''n'' football matches to be a homethat, drawregardless orof awaythe winoutcome, withhas at most ''R'' 'misses', by placing multiple bets that all ''n'' matches will end a certain way. Thus, for ''n'' matches with at most one 'miss', a ternary covering, ''K''<sub>3</sub>(''n'',1), is sought.
 
If <math>n=\tfrac12 (3^k-1)</math> then 3<sup>''n''-''k''</sup> are needed, so for ''n'' = 4, ''k'' = 2, 9 are needed; for ''n'' = 13, ''k'' = 3, 59049 are needed.<ref>http://alexandria.tue.nl/repository/freearticles/593454.pdf</ref> The best bounds known as of 2011<ref>http://www.sztaki.hu/~keri/codes/3_tables.pdf</ref> are