Decidability of the mixed quantifier fragment for powers of two and three
Determine whether the \(\exists^*\forall^*\) fragment of the first-order theory of \(\langle\mathbb{N};0,1,<,+,\{2^n:n\in\mathbb{N}\},\{3^n:n\in\mathbb{N}\}\rangle\) is decidable.
References
Decidability thus remains open for the $\exists* \forall*$ fragment.
— Rich Sequences and Decidability of Arithmetic Theories
(2609.20415 - Karimov et al., 17 Sep 2026) in Footnote in Section 1, State of the art for Problem 1