

A103317


Primes p such that p!  1 is also prime.


5




OFFSET

1,1


COMMENTS

The members are the primes in A002982 (n!  1 is prime).


REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, Section A2.


LINKS



EXAMPLE

3 is prime and 3!  1 = 5 is prime, so 3 is a member.


MATHEMATICA



PROG

(PARI) isok(n) = ispseudoprime(n) && ispseudoprime(n!1); \\ Jinyuan Wang, Jan 20 2020


CROSSREFS



KEYWORD

nonn,hard,more


AUTHOR



EXTENSIONS

a(5)=208003 (found on Jul 27 2016, by Sou Fukui), added by Jinyuan Wang, Jan 20 2020


STATUS

approved



