POWER SUMS ASSOCIATED WITH CERTAIN RECURSIVE PROCEDURES ON WORDS
The paper investigates classes of words equivalent under different ways of counting subwords. We present a general method of constructing sequences of equivalent words. Apart from obtaining numerical characterizations of words, we also construct sequences of words generating equal arithmetical power sums. Our notions of equivalence include the Parikh equivalence resulting from Parikh matrices, recently widely studied. Consequently, we are able to settle some open problems in this area.
power sum word equivalence subword scattered subword position of letter parikh matrix d0l system thue morphism