1
$\begingroup$

This question already has an answer here:

I came across the following question:

Is it known whether there exist infinitely many primes $p$ such that $\frac{p-1}{2}!\equiv_{p}1$?

(It is easy to see that if $p\equiv_{4}3$ then this number is $\pm 1$ mod $p$.)

$\endgroup$

marked as duplicate by Dietrich Burde, Yemon Choi, Lucia, Emil Jeřábek, Ramiro de la Vega Apr 28 '14 at 18:44

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Browse other questions tagged or ask your own question.