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Varieties generated by 2-testable monoids. (English) Zbl 1274.20057

A semigroup is 2-testable if it satisfies any identity formed by a pair of words that begin with the same letter, end with the same letter, and share the same set of factors of length two. It is shown that there are 28 monoid varieties generated by 2-testable monoids; all are finitely generated and 19 of them are finitely based.

MSC:

20M07 Varieties and pseudovarieties of semigroups
08B15 Lattices of varieties
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