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 $p$.)
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 $p$.)