Abstract
A sequence w over a finite alphabet A is generated by a uniform automaton if there exists an automaton labelled on {0,…,k − 1} for some k > 1 and recognizing for each output a in A the set of positions of a in w expressed in base k. Automatic sequences are generated by finite automata. By considering pushdown automata instead of finite ones, we generate exactly the context-free sequences. We distinguish the sub-families of unambiguous, deterministic, real-time deterministic context-free sequences associated with the corresponding families of pushdown automata. We study the closure under shift, product, morphisms, inverse substitutions and various extractions of these four families of context-free sequences. Additionally, we show that only using multiplicatively dependent bases yields the same set of context-free sequences.
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Caucal, D., Le Gonidec, M. (2014). Context-Free Sequences. In: Ciobanu, G., Méry, D. (eds) Theoretical Aspects of Computing – ICTAC 2014. ICTAC 2014. Lecture Notes in Computer Science, vol 8687. Springer, Cham. https://doi.org/10.1007/978-3-319-10882-7_16
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DOI: https://doi.org/10.1007/978-3-319-10882-7_16
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