Loading ...
Sorry, an error occurred while loading the content.

15759Re: another way to calculate primes

Expand Messages
  • Gianni Mazzarello
    Dec 12, 2004
      You say:
      --
      You have to count the "reverse" cases:

      ...1 => 1 x 1 or 3 x 7 or 7 x 3 or 9 x 9
      ...3 => 1 x 3 or 3 x 1 or 7 x 9 or 9 x 7
      ...7 => 1 x 7 or 7 x 1 or 3 x 9 or 9 x 3
      ...9 => 1 x 9 or 9 x 1 or 7 x 7 or 3 x 3
      --

      It seems to me you are right (more or less).
      But haven't they "reverse" cases also 1x1 and 3x3 and 7 x 7 and 9 x 9?
      Then we have to consider:


      ...1 => 1 x 1 or 3 x 7 or 7 x 3 or 9 x 9 or 1 x 1 or 9 x 9
      ...3 => 1 x 3 or 3 x 1 or 7 x 9 or 9 x 7
      ...7 => 1 x 7 or 7 x 1 or 3 x 9 or 9 x 3
      ...9 => 1 x 9 or 9 x 1 or 7 x 7 or 3 x 3 or 3 x 3 or 7 x 7

      Gianni

      ______________________________________________________
      ----- Original Message -----
      From: "Jens Kruse Andersen" <jens.k.a@...>
      To: "Mazzarello Gianni" <g.mazzarello@...>
      Sent: Friday, December 10, 2004 4:54 PM
      Subject: Re: another way to calculate primes


      Re: another way to calculate primes

      ----- Original Message -----
      From: "Mazzarello Gianni" <g.mazzarello@...>
      To: <primenumbers@yahoogroups.com>
      Sent: Friday, December 10, 2004 12:01 PM
      Subject: RE: [PrimeNumbers] another way to calculate primes



      > ...1 => 1 x 1 or 3 x 7 or 9 x 9
      > ...3 => 1 x 3 or 7 x 9
      > ...7 => 1 x 7 or 3 x 9
      > ...9 => 1 x 9 or 7 x 7 or 3 x 3

      You have to count the "reverse" cases:

      ...1 => 1 x 1 or 3 x 7 or 7 x 3 or 9 x 9
      ...3 => 1 x 3 or 3 x 1 or 7 x 9 or 9 x 7
      ...7 => 1 x 7 or 7 x 1 or 3 x 9 or 9 x 3
      ...9 => 1 x 9 or 9 x 1 or 7 x 7 or 3 x 3

      4 cases for each digit.

      --
      Jens Kruse Andersen (off list)
    • Show all 15 messages in this topic