Exercise 12:

K    {pIm(φp)=2}\overline{K}\;\leq\;\{ p \mid |\mathtt{Im}(\varphi_p)|=2 \}
Reduce K\overline{K} to the set of natural numbers codifying programs such that the image of the function computed by the program has cardinal 22 (roughly, the set of programs implementing functions whose image has exactly two elements) in order to prove that such set is not semi-decidable (not recursively enumerable).
Authors: Carles Creus, Guillem Godoy / Documentation:
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