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(Wenzel). Describe all subdirectly irreducible mono-unary algebras. [In particular show that they are countable.] Thanks!

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Source? What have you tried? – Potato Dec 24 '12 at 17:56
Welcome to MSE! You might not be aware, but there is definitely an etiquette to posing questions on this site. Also, is this homework? If so, it should be tagged as such. Your title is wrong and what have you tried? – Amzoti Dec 24 '12 at 17:56

A Monoid is a semi-group G containing an element e member of G so that each of the members of G and a = ae = ea, the element e of an element is the same for Tkvar G is called a (+, N) and (+, Z )

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This answer seems very garbled. Also, it's about monoids while the question was about mono-unary algebras, which are something quite different. – Andreas Blass Dec 31 '12 at 18:10

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