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last Saturday... (maximin prime dates)

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  • MICHAEL HARTLEY
    [ trivial but maybe fun ] Last Saturday may have been a special day in primedom. It may have been a maximin prime date. At least, using the American
    Message 1 of 1 , Nov 2, 2001
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      [ trivial but maybe fun ]

      Last Saturday may have been a special day in primedom.

      It may have been a "maximin" prime date. At least, using the
      American convention of putting the month first.

      Definitions: For a date with month a and day b, define the
      sequence N of all n>1 such that a*10^n+b is prime.

      If N is not empty, choose the minimum n in the sequence.

      Then, find the maximum over all dates of these minimal n.

      The dates which yield these maxima will be called "American
      maximin prime dates"

      Unless N is nonempty for the 1st of October, the only American
      maximin prime date is the 27th October. 10.10^n + 27 is prime for
      n=82, but composite for n=2,3,4,...,81

      If we similarly define "European maximin prime dates", with the
      month coming at the end, then (unless N is nonempty for the 10th
      of January), the only European maximin prime date is the 31st of
      January.

      31.10^n + 1 is prime for n=51, but composite for n=2,3,...,50.

      Do these get into the prime curios pages?? :-)

      Anyone whose birthday falls on (one of) these two dates??

      This email is inspired by a thread that occurred around the 4th of
      July.

      Yours, Mike H...


      Michael Hartley : Michael.Hartley@...
      Head, Department of Information Technology,
      Sepang Institute of Technology
      +---Q-u-o-t-a-b-l-e---Q-u-o-t-e----------------------------------
      "If you entertain a thought, it becomes an attitude..."
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