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 2007-01-19, 19:06 #12 michaf     Jan 2005 7378 Posts small succes: 91268055041 | 22^134217728+1 So at least THAT one isn't prime :)
2007-01-20, 00:43   #13
fatphil

May 2003

3·7·11 Posts

Quote:
 Originally Posted by michaf small succes: 91268055041 | 22^134217728+1 So at least THAT one isn't prime :)
That's about one millionth of a second's work. Why is it considered a success?

2007-01-20, 03:23   #14
jasong

"Jason Goatcher"
Mar 2005

350710 Posts

Quote:
 Originally Posted by fatphil That's about one millionth of a second's work. Why is it considered a success?
He's probably thinking of how long it would take to test the number for primality if it hadn't been sieved.

2007-01-20, 08:03   #15
michaf

Jan 2005

479 Posts

Quote:
 Originally Posted by jasong He's probably thinking of how long it would take to test the number for primality if it hadn't been sieved.
That was indeed what I was thinking :)
_and_ it took some 24 hours to get to that sieving point :>

2007-01-20, 08:20   #16
Citrix

Jun 2003

62B16 Posts

Quote:
 Originally Posted by michaf That was indeed what I was thinking :) _and_ it took some 24 hours to get to that sieving point :>
Should have taken you less than a sec!

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

Last fiddled with by Citrix on 2007-01-20 at 08:45

2007-01-20, 18:29   #17
michaf

Jan 2005

479 Posts

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:
 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.
I think this justifies the search

2007-01-20, 23:24   #18
michaf

Jan 2005

479 Posts

Quote:
 Originally Posted by Citrix Should have taken you less than a sec!
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?

2007-01-21, 02:34   #19
Citrix

Jun 2003

1,579 Posts

Quote:
 Originally Posted by michaf 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?
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.

 2007-01-21, 09:58 #20 michaf     Jan 2005 47910 Posts 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?
2007-01-21, 11:11   #21
Citrix

Jun 2003

62B16 Posts

Quote:
 Originally Posted by michaf 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?
Try PFGW.

2007-01-21, 12:54   #22
michaf

Jan 2005

479 Posts

Quote:
 Originally Posted by Citrix Try PFGW.
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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