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Re: Primes and Runsums

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  • Mark Underwood
    ... OK I get it now, he said sheepishly. I find it amazing the lengths I can go to misunderstand a problem! :) Thanks Jens. Mark
    Message 1 of 5 , Jun 25, 2008
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      --- In primenumbers@yahoogroups.com, "Jens Kruse Andersen" <jens.k.a@...> wrote:
      >
      > Ronald Dwyer wrote:
      > >> Using a run sum calculator website, I found the numbers in the range
      > >> 1 to 150 (this was arbitrary) that are the sums of exactly 2 runs.
      >
      > Mark Underwood wrote:
      > > From a cursory glance at the numbers Ronald has provided, this seems
      > > very remarkable to me.
      >
      > Maybe you didn't receive my post which explains it:
      > http://tech.groups.yahoo.com/group/primenumbers/message/19444
      > The key is that a runsum can be written as a product (where one of
      > the terms may be 1).
      >
      > > when I add two run sums together I get a number not on Ron's list:
      > >
      > > (2+3+4) + (6+7+8+9) = 39.
      >
      > Ronald meant numbers for which there are exactly two different runs
      > with the same sum, for example:
      > 41 = 41 (the sum of one number), and 41 = 20+21 (the sum of two numbers).
      > All odd numbers have these two sums. There are more sums if and
      > only if the number is composite, for example 39 = 12+13+14 = 4+5+6+7+8+9.
      >
      > --
      > Jens Kruse Andersen
      >

      OK I get it now, he said sheepishly. I find it amazing the lengths I can go to misunderstand
      a problem! :)

      Thanks Jens.

      Mark
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