Irreducibility of Polynomials with Square Coefficients over Finite Fields

We study a random polynomial of degree $n$ over the finite field ${\mathbb{F}}_q$, where the coefficients are independent and identically distributed and uniformly chosen from the squares in ${\mathbb{F}}_q$. Our main result demonstrates that the likelihood of such a polynomial being irreducible approaches $1\mathrm{/}n+O(q^{-1\mathrm{/}2})$ as the field size $q$ grows infinitely large. The analysis we employ also applies to polynomials with coefficients selected from other specific sets.