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the 357 rule

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  • Bill Bouris
    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
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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 composite.  I could only go
      so far with my outdated computer and UBasic. Can anyone find a counter-example ???
      Bill
    • Paul Leyland
      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
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        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 so far with my outdated computer and UBasic.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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