## the 357 rule

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• Group, I believe that if N passes the 2-PRP test that either 3, 5, or 7 divides N-1 , one or all of them, or N will be divisible by 3, 5, or 7 and be
Message 1 of 2 , Feb 1, 2010
Group,
I believe that if 'N' passes the 2-PRP test that either 3, 5, or 7 divides 'N-1', one or
all of them, or 'N' will be divisible by 3, 5, or 7 and be composite.  I could only go
so far with my outdated computer and UBasic. Can anyone find a counter-example ???
Bill
• If you used your elderly computer to search for known results rather than for computations you would have discovered
Message 2 of 2 , Feb 1, 2010
If you used your elderly computer to search for known results rather
than for computations you would have discovered
http://www.research.att.com/~njas/sequences/A055550 and, in particular,
the entry 264239

264239 = 139 * 1901
264238 = 2 * 13 * 10163

Paul

On Mon, 2010-02-01 at 06:18 -0800, Bill Bouris wrote:
>
> Group,
> I believe that if 'N' passes the 2-PRP test that either 3, 5, or 7
> divides 'N-1', one or
> all of them, or 'N' will be divisible by 3, 5, or 7 and be composite.
> I could only go
> so far with my outdated computer and UBasic. Can anyone find a
> counter-example ???
> Bill
>
>
>
>
>
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