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Gottfried Helms science forum Guru
Joined: 24 Mar 2005
Posts: 301

Posted: Fri Jul 29, 2005 11:50 am Post subject:
Re: primality preserving function?



Jim Spriggs schrieb::
Quote:  gsax wrote:
Define formula.
Ok, so I have to define what I mean by a formula..!
well that is a tough one... but let me try to say that the formula
shall consist only of addition/subtraction, multiplication/division,
exponentiation...
Then I think your quest is a hopeless one. At present.

a bit out of seriousness... ;)
f(x) = {log(x+1)/log(2) iff the result is a positive integer
{ 0 else
Gottfried Helms 

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gsax science forum beginner
Joined: 12 Jul 2005
Posts: 44

Posted: Sat Jul 16, 2005 3:44 am Post subject:
primality preserving function?



Hi
I was trying to come up with a function that is primality
preserving..i.e. let the function be f(x)...then I want
f(x) > x
&
f(x) is prime iff x is prime...
I have not been able to produce such a function...
I would like to know , if anyone has a example of such a function..
best regards
Gsax 

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