Counting Polynomials with Distinct Roots Using Subset Sum
摘要
Given a finite abelian group G, a finite set D, and a mapping \(f:D\rightarrow G\) , we find the number of r-subsets \(S\subseteq D\) where for \(b\in G\) , \(\begin{aligned} \sum _{x\in S}f(x)=b. \end{aligned}\) We count degree n monic polynomials over \({\mathbb {F}}_q\) with r distinct roots in a set \(D\subseteq {\mathbb {F}}_q\) when the leading terms of degree at least \(n-\ell \) are fixed. We obtain new formulas for \(\ell =2\) when D is an arbitrary subfield of \({\mathbb {F}}_q\) with q odd.