Let R be a finite commutative ring. The set F(R)\documentclass[12pt]{minimal}
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\begin{document}$${{\mathcal{F}}}(R)$$\end{document} of polynomial functions on R is a finite commutative ring with pointwise operations. Its group of units F(R)×\documentclass[12pt]{minimal}
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\begin{document}$${{\mathcal{F}}}(R)^\times $$\end{document} is just the set of all unit-valued polynomial functions. We investigate polynomial permutations on R[x]/(x2)=R[α]\documentclass[12pt]{minimal}
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\begin{document}$$R[x]/(x^2)=R[\alpha ]$$\end{document}, the ring of dual numbers over R, and show that the group PR(R[α])\documentclass[12pt]{minimal}
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\begin{document}$${\mathcal{P}}_{R}(R[\alpha ])$$\end{document}, consisting of those polynomial permutations of R[α]\documentclass[12pt]{minimal}
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\begin{document}$$R[\alpha ]$$\end{document} represented by polynomials in R[x], is embedded in a semidirect product of F(R)×\documentclass[12pt]{minimal}
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\begin{document}$${{\mathcal{F}}}(R)^\times $$\end{document} by the group P(R)\documentclass[12pt]{minimal}
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\begin{document}$${\mathcal{P}}(R)$$\end{document} of polynomial permutations on R. In particular, when R=Fq\documentclass[12pt]{minimal}
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\begin{document}$$R={\mathbb{F}}_q$$\end{document}, we prove that PFq(Fq[α])≅P(Fq)⋉θF(Fq)×\documentclass[12pt]{minimal}
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\begin{document}$${\mathcal{P}}_{{\mathbb{F}}_q}({\mathbb{F}}_q[\alpha ])\cong {\mathcal{P}}({\mathbb{F}}_q) \ltimes _\theta {{\mathcal{F}}}({\mathbb{F}}_q)^\times $$\end{document}. Furthermore, we count unit-valued polynomial functions on the ring of integers modulo pn\documentclass[12pt]{minimal}
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\begin{document}$${p^n}$$\end{document} and obtain canonical representations for these functions.
