Farey=: x:@/:~@(0 , ~.)@(#~ <:&1)@:,@(%/~@(1 + i.))      NB. calculates Farey sequence
displayFarey=: ('r/' charsub '0r' , ,&'r1')@":           NB. format character representation of Farey sequence according to task requirements
order=: ': ' ,~ ":                                       NB. decorate order of Farey sequence