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RE: a really cool problem to solve that will teach alot about primes

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  • Jon Perry
    (readbaby2000@yahoo.com does not exist) The address for the group is: primenumbers@yahoogroups.com You should use this address to post a new thread. To comment
    Message 1 of 3 , Jul 29, 2002
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      (readbaby2000@... does not exist)

      The address for the group is:

      primenumbers@yahoogroups.com

      You should use this address to post a new thread.

      To comment and reply to an existing thread, hit 'Reply to All'. This ensures
      your message goes to the entire group. Hitting 'Reply' only replies to the
      original sender.

      >c=0;for (n=1,1000,if (sigma
      (n,0)%2==0,c++);print(c)

      is Pari/GP code. Pari/GP is an excellent and powerful calculator, avaiable
      for free from:

      http://www.gn-50uma.de/ftp/pari/00index.html

      tau(n) is the count of the number of divisors of n.

      If n=p1^e1..pk^ek,

      then tau(n)=(e1+1)...(ek+1)

      e.g. 12=2^2.3, tau(12)=(2+1)(1+1)=6

      which means that 12 has 6 divisors, namely 1,2,3,4,6 and 12.

      iff tau(n) is even

      means that if tau(n) is even then the door is closed, else the door is open
      (iff means if and only if).

      Hope this helps.

      Jon Perry
      perry@...
      http://www.users.globalnet.co.uk/~perry/maths
      BrainBench MVP for HTML and JavaScript
      http://www.brainbench.com


      -----Original Message-----
      From: readbaby2000 [mailto:readbaby2000@...]
      Sent: 29 July 2002 18:21
      To: Jon Perry
      Subject: Re: a really cool problem to solve that will teach alot about
      primes


      hi, i wanted to know how to post messeges to the group. when i posted
      the problem with the lockers, i meant it to be for the whole group.
      only you got the messege. how do i post?
      also, i think you solved the problem but i cant tell because of the
      language you used. what in the world does "iff tau" mean? and sigma,
      tau(n) in fact i dont get this whole line:(c=0;for (n=1,1000,if (sigma
      (n,0)%2==0,c++);print(c))
      i think you got it though. but can u please explain it in english?
      thanx






      Jon Perry
      perry@...
      http://www.users.globalnet.co.uk/~perry/maths
      BrainBench MVP for HTML and JavaScript
      http://www.brainbench.com


      -----Original Message-----
      From: readbaby2000 [mailto:readbaby2000@...]
      Sent: 29 July 2002 18:21
      To: Jon Perry
      Subject: Re: a really cool problem to solve that will teach alot about
      primes


      hi, i wanted to know how to post messeges to the group. when i posted
      the problem with the lockers, i meant it to be for the whole group.
      only you got the messege. how do i post?
      also, i think you solved the problem but i cant tell because of the
      language you used. what in the world does "iff tau" mean? and sigma,
      tau(n) in fact i dont get this whole line:(c=0;for (n=1,1000,if (sigma
      (n,0)%2==0,c++);print(c))
      i think you got it though. but can u please explain it in english?
      thanx
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