A factorial prime is a prime number that is one less or one more than a factorial.
The first 10 factorial primes are:
2, 3, 5, 7, 23, 719, 5039, 39916801, 479001599, 87178291199, ...
n! Wikipedia
Conjectured no. of terms: Infinite
First terms: 2, 3, 5, 7, 23, 719, 5039, 39916801, 479001599, 87178291199
Largest known term: 422429! + 1
No. of known terms: 52