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arXiv · 2507.18589

Evaluation of a determinant involving Legendre symbols

Chen-Kai Ren·Zhi-Wei Sun
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Abstract

Let $p>3$ be a prime, and let $(\frac{\cdot}p)$ be the Legendre symbol. Let $A_p(x)$ denote the matrix $[x+a_{ij}]_{1\leqslant i,j\leqslant (p-1)/2}$, where $$ a_{ij}=\begin{cases} (\frac{j}{p}) &\text{if} \ i=1, \$\frac{i+j}{p}) &\text{if} \ i>1. \end{cases}$$ In 2018 Z.-W. Sun conjectured that $\det A_p(0)=-2^{(p-3)/2}$ if $p\equiv 3 \pmod{4}$, which was later confirmed by G. Zaimi. In this paper we evaluate $\det A_p(x)$ completely.

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Chen-Kai Ren, Zhi-Wei Sun. 2025-07-24. Evaluation of a determinant involving Legendre symbols. https://arxiv.org/abs/2507.18589

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