We proved that there are no polynomials ∈ ℚ, deg is odd, deg ≥ 7, deg ≠ 11,13, for which the corresponding hyperelliptic field ℚ()(√) has a fundamental -unit of degree 13 and for which the expansion of √ into a functional continued fraction is periodic. In the case deg = 11,13, all polynomials with the indicated properties are obtained. It is also proved that there exist at most finitely many pairwise nonequivalent polynomials () ∈ ℚ of degree 5 with such properties. Symbolic computations with Grobner bases play a significant role in proving the main results.
Platonov et al. (Wed,) studied this question.