A classification of disjoint unions of two or three copies of the free monogenic semigroup
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Author
Abu-Ghazalh, N.
Mitchell, J. D.
Péresse, Y.
Ruškuc, N.
Attention
2299/19000
Abstract
We prove that, up to isomorphism and anti-isomorphism, there are only two semigroups which are the union of two copies of the free monogenic semigroup. Similarly, there are only nine semigroups which are the union of three copies of the free monogenic semigroup. We provide finite presentations for each of these semigroups.