

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

Table of n, a(n) for n=1..5.
Eric Weisstein's World of Mathematics, Factorial Prime
Index entries for sequences related to factorial numbers.


EXAMPLE

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


MATHEMATICA

Select[Prime[Range[100]], PrimeQ[#!  1] &] (* Vladimir Joseph Stephan Orlovsky, Feb 01 2012 *)


PROG

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


CROSSREFS

Cf. A002982, A093804.
Sequence in context: A064774 A089689 A248701 * A104051 A128004 A281889
Adjacent sequences: A103314 A103315 A103316 * A103318 A103319 A103320


KEYWORD

nonn,hard,more


AUTHOR

Jonathan Sondow, Jan 31 2005


EXTENSIONS

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


STATUS

approved



