Meta-Automatic Sequences
John M. Campbell
Department of Mathematics and Statistics
Dalhousie University
Halifax, NS B3H 4R2
Canada
Benoît Cloitre
19, rue Louise Michel
92300 Levallois-Perret
France
Abstract:
Nested (or meta-Fibonacci) recurrences, such as the
recurrence used to define Hofstadter's Q-sequence, along with the
digit-based recurrences that underlie automatic sequences are of
interest from both number-theoretic and combinatorial points of view. In
this direction, Allouche and Shallit showed how the frequency sequence
of a variant of the Q-sequence is 2-automatic. This inspires
us to introduce what may be seen as a natural combination of the
recurrences for meta-Fibonacci and automatic sequences, by introducing
the concept of a meta-automatic sequence. We exhibit two binary
meta-automatic sequences ℳ1 and ℳ2 whose
defining recurrences do not satisfy the Allouche-Shallit automaticity
criterion directly, and this is formalized in our paper. For each of
these integer sequences ℳ1 and ℳ2, we prove
explicit DFAO evaluations, together with 4-uniform morphisms, and we
also consider the factor complexities of these sequences.
Full version: pdf,
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(Concerned with sequences
A005185
A039982
A244477
A298952
A391614
A392736.)
Received March 2 2026;
revised version received May 26 2026.
Published in Journal of Integer Sequences,
June 4 2026.
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