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Re: [PrimeNumbers] strange news

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  • Jens Kruse Andersen
    ... It depends what you mean by real. It works correctly and he may be the first to publish this particular formula, but useless prime formulas based on
    Message 1 of 6 , Nov 8, 2008
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      Alex Petty wrote:
      > let me ask again.
      > is this a real discovery? i didn't follow the previous explanation.

      It depends what you mean by real. It works correctly and he may be the first
      to publish this particular formula, but useless prime formulas based on
      Wilson's theorem are common.
      The discoverer added mention of it to Wikipedia in June 2007.
      I removed it with an edit summary pointing to Wikipedia policies and ending
      "Looks trivial, useless, non-notable":
      http://en.wikipedia.org/w/index.php?title=Formula_for_primes&diff=next&oldid=136831799

      At the time I checked that the formula actually works.
      It uses the well-known Wilson's theorem (apparently first discovered by the
      Arabian mathematician Ibn al-Haytham around year 1000) to test whether 2m+1
      is an odd prime. If it is then 2m+1 is produced, otherwise 2. Instead of
      writing this as a simple if-then-else, it uses a complicated formula with
      the floor function to avoid direct use of an if-then-else construct which is
      sometimes not considered an allowed part of a "formula".

      --
      Jens Kruse Andersen
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