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From: Richard L. Peterson on 22 Jan 2010 10:33
I just read this in abook by William Stein.

Thanks
From: Andrew Usher on 22 Jan 2010 20:54
On Jan 22, 7:33 pm, "Richard L. Peterson" <rl_p...(a)yahoo.com> wrote:
> I just read this in abook by William Stein.

If he considers +1 a prime also, then -1 must be.
But if he considers only -1 a prime, presumably it's because one can
extend a type of unique factorisation to the negative numbers i.e.
they equal -1 times the positive number.

Andrew Usher
From: Chip Eastham on 22 Jan 2010 21:09
On Jan 22, 8:33 pm, "Richard L. Peterson" <rl_p...(a)yahoo.com> wrote:
> I just read this in abook by William Stein.
>
> Thanks

I suspect a misunderstanding has crept into the
discussion. -1 is not considered a prime. However
in quadratic sieving methods for large factoring
problems, it can be advantageous to include -1 as
a "small factor" of squares modulo the composite
to be factored.

regards, chip
From: Henry on 22 Jan 2010 21:11
On 23/01/2010 01:33, Richard L. Peterson wrote:
> I just read this in abook by William Stein.
>
> Thanks

No idea, but perhaps its only two divisors are 1 and itself
From: Richard L. Peterson on 22 Jan 2010 11:25
> On Jan 22, 7:33 pm, "Richard L. Peterson"
> <rl_p...(a)yahoo.com> wrote:
> > I just read this in abook by William Stein.
>
> If he considers +1 a prime also, then -1 must be.
> But if he considers only -1 a prime, presumably it's
> because one can
> extend a type of unique factorisation to the negative
> numbers i.e.
> they equal -1 times the positive number.
>
> Andrew Usher

good suggestion, maybe that's it. But maybe not.
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