In this work, we study a numeral system with a natural base $s \geq 2$ and a redundant alphabet $A_r=\{ 0,1, \dots, r\}$, where $s \leq r \leq 2s-2$. We investigate the topological, metric, and fractal properties of the set of numbers in the interval $\left[0,\frac{ r}{ s-1}\right]$ that admit a unique representation $x=\sum\limits_{ n=1}^{ \infty}\frac{ \alpha_n} { s^n}\equiv\Delta^{ r_s}_{ \alpha_1\alpha_2...\alpha_n...}$, $\alpha_n\in A_r$. The criterion for the uniqueness of the number representation is established. It is proved that the Hausdorff--Besicovitch dimension of the set of numbers with a unique representation is equal to $\frac{ \ln(2s-r-1)}{ \ln s}$. An analysis of the quantity of representations of numbers having purely periodic representations with a simple period (a single-digit period) is carried out. It is proved that the set of numbers that admit a continuum of distinct representations has full Lebesgue measure. Conditions for a number to belong to this set are given in terms of one of its representations.
Categories: math.NT