OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..202 (terms below 10^15)
Mersenne Forum, Composite PRP (discussion thread).
EXAMPLE
10974881 is in the sequence because it divides 2^239 - 1 (and 239 is prime), it is not a prime, but 3^10974880 === 1 (mod 10974881).
PROG
(PARI) forstep(n=3, +oo, 2, Mod(3, n)^(n-1)==1&&!ispseudoprime(n)&&ispseudoprime(znorder(Mod(2, n)))&&print1(n, ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Jeppe Stig Nielsen, May 11 2019
STATUS
approved