For with odd and , if there exists an integer such that

then is prime. A prime of this form is known as a Proth prime.

For with odd and , if there exists an integer such that

then is prime. A prime of this form is known as a Proth prime.

Weisstein, Eric W. "Proth's Theorem."
From *MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/ProthsTheorem.html