Sierpinski / Riesel - Base 22

[michaf]

small succes:

91268055041 | 22^134217728+1

So at least THAT one isn't prime :)

[fatphil]

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?

[jasong]

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.

[michaf]

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 :>

[Citrix]

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

[michaf]

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?

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.

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

[michaf]

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?

[Citrix]

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.

[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?

[Citrix]

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.

[michaf]

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?