Completing the picture for the Skolem Problem on order-4 linear recurrence sequences
Formal Languages and Automata Theory
2025-12-10 v5 Number Theory
Abstract
For almost a century, the decidability of the Skolem Problem - that is, the problem of finding whether a given linear recurrence sequence (LRS) has a zero term - has remained open. A breakthrough in the 1980s established that the Skolem Problem is indeed decidable for algebraic LRS of order at most 3, and real algebraic LRS of order at most 4. However, for general algebraic LRS of order 4 the question of decidability has remained open. Our main contribution in this paper is to prove decidability for this last case, i.e. we show that the Skolem Problem is decidable for all algebraic LRS of order at most 4.
Cite
@article{arxiv.2409.01221,
title = {Completing the picture for the Skolem Problem on order-4 linear recurrence sequences},
author = {Piotr Bacik},
journal= {arXiv preprint arXiv:2409.01221},
year = {2025}
}
Comments
11 pages. This is the TheoretiCS journal version