OFFSET
1,1
COMMENTS
An Euler-Jacobi pseudoprime to the base b is an odd composite number k such that gcd(b, k) = 1 and the Jacobi symbol (.,.) satisfies b^((k-1)/2) == (b,k) (mod k).
a(n) is coprime to A002110(n-1).
a(24) > 2^64. - Daniel Suteu, Jun 05 2022
LINKS
Eric Weisstein's World of Mathematics, Euler-Jacobi Pseudoprime.
PROG
(PARI) a(n) = my(b, p=factorback(primes(n-1))); forcomposite(k=9, oo, if(gcd(k, p)==1, b=2; while(Mod(b, k)^(k\2) == kronecker(b, k), b++); if(b==prime(n), return(k))));
CROSSREFS
KEYWORD
nonn
AUTHOR
Jinyuan Wang, Jun 03 2022
EXTENSIONS
a(13)-a(23) from Daniel Suteu, Jun 05 2022
STATUS
approved