login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103317 Primes p such that p! - 1 is also prime. 5
3, 7, 379, 6917, 208003 (list; graph; refs; listen; history; text; internal format)
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
Eric Weisstein's World of Mathematics, Factorial Prime
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
Sequence in context: A348376 A089689 A248701 * A104051 A128004 A281889
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 2 00:03 EST 2024. Contains 370447 sequences. (Running on oeis4.)