In a message dated 18/10/98 09:44:32, you write:
<<
At 12:59 AM 10/17/98 -0400, Foghorn Leghorn wrote:
>
>Second, I see that there are now some composite exponents in the ECM
>factoring page. Why are none of them even? Is there a technical reason
>that makes them less interesting?
Composite exponents have algebraic factors. For even n, 2^n-1 is divisible
by
3.
>>
Also, for even n, 2^n-1 is identical to (2^(n/2)-1)*(2^(n/2)+1)
Check it out!
n 6 8 10 12
2^n-1 63 255 1023 4095
Factors 7.9 15.17 31.33 63.65
So for factoring even n values, the task is equivalent to
factoring 2^(n/2)+1 and 2^(n/2)-1 where n will be odd.
So we only need to bother wirth odd n values.
All the best, George.
