>
> The cofactor of F25 (after dividing out all the known factors) is
> currently 'status unknown', isn't it?.
>
> So it might be worth testing for compositeness. However at present there
> seems to be no way of proving it prime if it fails the compositeness
> test.
Tony,
Actually the status of F24 is unknown. F25 has three known factors.
F25 = (48413*2^29 +1)(1522849979*2^27+1)(16168301139*2^27+1)*C33554349
If Pepin's primality test was run on F24, we could determine if F24 was
composite or prime. The chances that F24 is a psuedo-prime (a composite
pretending to be a prime) are very slim so it is worth the time to run the
test. I estimate the time required would be 6-9 months and we could do it with
existing software.
Chip Kerchner
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