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-   -   Sierpinski / Riesel - Base 22 (https://www.mersenneforum.org/showthread.php?t=6916)

michaf 2007-01-19 19:06

small succes:

91268055041 | 22^134217728+1

So at least THAT one isn't prime :)

fatphil 2007-01-20 00:43

[QUOTE=michaf;96539]small succes:

91268055041 | 22^134217728+1

So at least THAT one isn't prime :)[/QUOTE]

That's about one millionth of a second's work. Why is it considered a success?

jasong 2007-01-20 03:23

[QUOTE=fatphil;96571]That's about one millionth of a second's work. Why is it considered a success?[/QUOTE]
He's probably thinking of how long it would take to test the number for primality if it hadn't been sieved.

michaf 2007-01-20 08:03

[QUOTE=jasong;96577]He's probably thinking of how long it would take to test the number for primality if it hadn't been sieved.[/QUOTE]

That was indeed what I was thinking :)
_and_ it took some 24 hours to get to that sieving point :>

Citrix 2007-01-20 08:20

[QUOTE=michaf;96590]That was indeed what I was thinking :)
_and_ it took some 24 hours to get to that sieving point :>[/QUOTE]

Should have taken you less than a sec!:smile:

Anyway why are you trying to factorize these numbers
For base 22, numbers that are multiple of 22 do not have to be tested, this eliminates k=22,484 but k=1 is left. But 1*22^1+1 is prime hence 1 is eliminated.

under base=100 only the following bases are left for which k does not produce a prime
38
50
62
68
86
92
98
You can try to find a prime for them

michaf 2007-01-20 18:29

[quote]
Originally Posted by michaf View Post
Without any math skills... so excuse me if I bugger here :>

base 22:

22*22^n + 1
=
22^(n+1) + 1
=
1*22^(n+1) + 1

so, k = 1
and that one is eliminated, therefore is k=22 and 484?[/quote]

[quote]
Unfortunately not. 1*22^1+1=23 prime, but, I think we decided for the Sierpinski base 5 exercise, that we would not use n=0, otherwise k=22 could be eliminated but not 484.[/quote]

(quotes from sierpinski 6-18 thread)
I think this justifies the search

michaf 2007-01-20 23:24

[QUOTE=Citrix;96592]Should have taken you less than a sec!:smile:
[/QUOTE]

Oh, how do you do that? Test for all factors upto that limit in a sec? :)
Or did you mean just testing if that one number divided the huge number?

Citrix 2007-01-21 02:34

[QUOTE=michaf;96643]Oh, how do you do that? Test for all factors upto that limit in a sec? :)
Or did you mean just testing if that one number divided the huge number?[/QUOTE]

Finding the factor should take less than 1 sec. Try to factor 1 number at a time. What numbers are left, I can try to prove them composite them for you.

michaf 2007-01-21 09:58

Hmm... what am I doing wrong then?

srsieve is sieving about 20-30Million p's per second, but not a huge amount more when sieving only 1 n.
Or is srsieve the wrong program here?

Citrix 2007-01-21 11:11

[QUOTE=michaf;96674]Hmm... what am I doing wrong then?

srsieve is sieving about 20-30Million p's per second, but not a huge amount more when sieving only 1 n.
Or is srsieve the wrong program here?[/QUOTE]

Try PFGW.

michaf 2007-01-21 12:54

[QUOTE=Citrix;96679]Try PFGW.[/QUOTE]

I couldn't notice anything quicker about pfgw's factoring routines then there is in srsieve (quite the opposite, actually).

What's pfgw's command to find "91268055041 | 22^134217728+1" quickly?


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