mersenneforum.org

mersenneforum.org (https://www.mersenneforum.org/index.php)
-   Math (https://www.mersenneforum.org/forumdisplay.php?f=8)
-   -   Are the factors of high perfect numbers known? (https://www.mersenneforum.org/showthread.php?t=12179)

Primeinator 2009-07-22 23:00

[QUOTE=David John Hill Jr;182267]I had been meaning to post this elsewhere , but this looks like a better place.

Of very rare occurence and usage.

Begin at (p-1)!+1= K*p (AS befitting Wilson's theorem.)

Perform K+1, then as given 2^p-1 and a corresponding 2^(p-1), then
2^(p-1) | K+1

In reverse , as an integer multiple of 2^(p-1) subtract 1, and one has K, the
Wilson's theorem proof coefficient.

Two cases where this appears to hold(and possibly on up by induction)
is 2^3-1 and 2^7-1.(and should therefor really be included in the given statement)


As 'academic' to the whole picture that this may appear, they are(exist) cases
where going the perfect way should be a lot faster than full scale wilson calculation.[/QUOTE]

Doesn't this still require knowing the value of p?

Primeinator 2009-07-23 01:30

Additionally, if we consider
[tex](2^p -1)(2^{p-1})=\sum_{i=0}^{p-1} {2^i} + \sum_{j=0}^{p-2} {2^j(2^p-1)}[/tex]

then the number of distinct factors for the associated perfect number of any Mersenne prime can be given by:

factors = 1 + (p-1) + 1 + (p-2) + 1 = (2p-3) + 3 = [B]2*p[/B] factors

Just something interesting I just noticed.

Kevin 2009-07-23 07:20

[QUOTE=Primeinator;182298]Additionally, if we consider
[tex](2^p -1)(2^{p-1})=\sum_{i=0}^{p-1} {2^i} + \sum_{j=0}^{p-2} {2^j(2^p-1)}[/tex]

then the number of distinct factors for the associated perfect number of any Mersenne prime can be given by:

factors = 1 + (p-1) + 1 + (p-2) + 1 = (2p-3) + 3 = [B]2*p[/B] factors

Just something interesting I just noticed.[/QUOTE]

That's pretty easy to see directly. Assuming 2^{p}-1 is prime, all of your factors are either one of $p$ powers of 2 (2^0,2^1,/ldots, 2^{p-1}), or one of $p$ powers of two times the associated Mersenne prime ((2^0*(2^{p}-1),2^1*(2^{p}-1),/ldots, 2^{p-1}*(2^{p}-1)), for $2p$ distinct factors.

/too drunk to bother with the tex tags

David John Hill Jr 2009-07-23 08:09

In response to 2nd to last entry
 
To clarify, I was not suggesting a shortcut for a search for a p in general. The examples are just that , as occuring.For examples much higher the numbers are too great to verify with my software, and so , to verify a pattern
of the division by some 2^(p-1), as going this way.
I was simply noting the occurence of the +1 to the K of Wilson and division
by the 2^(p-1) as being another whole number, and further as far as computing it might be a faster way around.


As to the original thread post, back to the last entry--------


All times are UTC. The time now is 08:21.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.