infinite sequence {a_r ∶r≥1} of digits,which can be taken as 0 or 1, is periodic if, for some k ≥ 1, a_(r+k)= a_r for all r ≥ 1infinite sequence {a_r ∶r≥1} of digits,which can be taken as 0 or 1, is periodic if, for some k ≥ 1, a_(r+k)= a_r for all r ≥ 1