Furthermore, it is shown among others in [3]: (i) when the values xi are ofthe form 357
as above, then at least eleven values xi are needed, and 135 is the smallest possible largest
denominator; (ii) whenever the values xi are odd, the smallest possible value for k is 9 and
with that k the smallest x9 is 231.
The following question [2, Question 6] was independently raised by Burshtein [1] and
Graham [7].