LECTURE NOTES IN ANALYSIS (2011)
《LECTURE NOTES IN ANALYSIS (2011)》 · 第 100 页 · Section 2.8「Primitive Roots and Power Residues」，Definition 2.8
If $(a,p)=1$ and $x^n\equiv a\pmod p$ has a solution, then $a$ is called an $n$th power residue modulo $p$.