The number of bases in which
is a repeating decimal (actually, repeating
-ary) of length
is the same as the number of fractions
,
, ...,
which have reduced denominator
. For example, in bases 2, 3, ..., 6, 1/7 is given by
which have periods 3, 6, 3, 6, and 2, respectively, corresponding to the denominators 6, 3, 2, 3, and 6 of
 |
(6)
|