[GAP Forum] IsPrime

[Bill Allombert]

On Thu, Jun 09, 2005 at 02:28:57PM +0700, Vdovin Evgenii wrote:
> Dear pubbers!
> 
> I wonder if anybody knows what algorithm is used in GAP to check whether
> a given integer is prime.  Does anybody know another program that can
> check whether a given integer is prime? Now I'm considering a prime
> p=2^44497-1 and the problem is to check if p^2-p+1 is prime.

Hello Vdovin,
I have checked with PARI/GP isprime() function and q=p^2-p+1 is not prime.
For example, '2^(q-1) = 1 mod q' is false

Cheers,
Bill.