fcn farey(n){
   f1,f2:=T(0,1),T(1,n);  // fraction is (num,dnom)
   print("%d/%d %d/%d".fmt(0,1,1,n));
   while(f2[1]>1){
      k,t  :=(n + f1[1])/f2[1], f1;
      f1,f2 = f2,T(f2[0]*k - t[0], f2[1]*k - t[1]);
      print(" %d/%d".fmt(f2.xplode()));
   }
   println();
}