Denis McMahon wrote:
> Note also that when searching for factors of a number n, and starting at
> 2, you can generally stop at somewhere around n/3,
The largest factor of N you actually need to check is sqrt(n). Every factor
of n below the square root has a corresponding factor above it, e.g. if
On Sat, Sep 6, 2014 at 8:38 PM, Steven D'Aprano
wrote:
> 3, 5, 7, 9 is a waste of time, 11, 13, 15 is a waste of time, ...
I love this sequence.
ChrisA
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On 09/06/14 at 08:38pm, Steven D'Aprano wrote:
> But even that's not how the specialists do it. If you want to check whether
> (say) 2**3000+1 is prime, you don't want to use trial division at all...
When I was interested in these things, specialists would use the [number
field sieve](https://en.w
On Sat, 6 Sep 2014 12:53:16 +0200, Manolo Martínez wrote:
> On 09/06/14 at 08:38pm, Steven D'Aprano wrote:
>> But even that's not how the specialists do it. If you want to check whether
>> (say) 2**3000+1 is prime, you don't want to use trial division at all...
>
> When I was interested in these th
On 09/07/14 at 06:53pm, Peter Pearson wrote:
> On Sat, 6 Sep 2014 12:53:16 +0200, Manolo Martínez wrote:
> > On 09/06/14 at 08:38pm, Steven D'Aprano wrote:
> >> But even that's not how the specialists do it. If you want to check whether
> >> (say) 2**3000+1 is prime, you don't want to use trial div
On Sun, Sep 7, 2014 at 11:53 AM, Peter Pearson
wrote:
> On Sat, 6 Sep 2014 12:53:16 +0200, Manolo Martínez wrote:
>> On 09/06/14 at 08:38pm, Steven D'Aprano wrote:
>>> But even that's not how the specialists do it. If you want to check whether
>>> (say) 2**3000+1 is prime, you don't want to use tr