20030905, 05:53  #1 
Cranksta Rap Ayatollah
Jul 2003
641 Posts 
Catalan sequence (is C5 prime?)
is anybody putting any work in on this? ran across it on the Prime Pages
sure, the exponent is 170141183460469231731687303715884105727, but it seems like if anybody was going to bang away at it, it would be someone in here.[/url] 
20030905, 15:29  #2 
Sep 2002
106_{16} Posts 
Hi Travist,
Look further on the prime page you'll see the link to http://www.ltkz.demon.co.uk/ar2/mm61.htm Tony Forbes search for factors Joss[/url] 
20030905, 15:42  #3 
Jan 2003
North Carolina
2×3×41 Posts 
This is M170141183460469231731687303715884105727.
*If* prime95 could handle a number that large (C5 is much, much larger then prime95's maximum (somewhere around M77000000)), I suspect with current technology it would take a century or two to compute (or is that a millenium or two?); that is, of course, if the current technology could even begin to handle a number this large. 
20030905, 16:15  #4 
Cranksta Rap Ayatollah
Jul 2003
641 Posts 
just for clarification, I didn't expect anyone to be trying to prove primality, just looking for factors. Thanks for the link, jocylenl

20031001, 15:06  #5 
Jun 2003
3056_{8} Posts 
M?
What number will be MM127 expected to be for example the MP 40 is currently being searched.
Citrix 
20031002, 17:32  #6  
"Richard B. Woods"
Aug 2002
Wisconsin USA
2^{2}·3·641 Posts 
Quote:
The exponent is more than 2*10^30 times Prime95's current maximum exponent (79,300,000). 2*10^30 > 2^100. Doubling the exponent multiplies the execution time by more than a factor of 2, so multiplying the exponent by 2^100 raises the time by more than 2^100. We're talking about longer than nonillions (1 nonillion = 1 trillion * 1 billion * 1 billion) of years. Quote:
Giga = 10^9 Tera = 10^12 Peta = 10^15 Exa = 10^18 Zetta = 10^21 Yotta = 10^24 Need those petayottabyte memory sticks. Last fiddled with by cheesehead on 20031002 at 17:35 

20031002, 17:50  #7 
"Richard B. Woods"
Aug 2002
Wisconsin USA
2^{2}·3·641 Posts 
(Curses on the %$$& 5minute editing deadline!
Yeah, I know it's for the greater good.) My nonillionyear estimate was based on just the ratio of times for single LL iterations. There's an additional factor of 2*10^30 on the number of iterations required. So it's 2*10^30 nonillion years. But ... if there's a "Moore's Law"yerish doubling of speeds every 18 months ... Oh, someone _else_ figure that one! 
20031002, 20:42  #8 
Aug 2002
Portland, OR USA
2·137 Posts 
Well, my lunch napkin is too small for working that one out.
But we can say that Moore's "Law" implies it is a waste of time to start now, since using next years machine will save more than a year of time ... That argument does make sense in this case, because passing this problem from today's machine to next years would be fairly difficult. Switching machines in the middle of an LL this big is impossible, for factoring it would be merely "challenging". 
20031002, 21:18  #9 
Bemusing Prompter
"Danny"
Dec 2002
California
95C_{16} Posts 
And by several decades, we'll probably have quantum computers that can factor MM127 in less than a second...

20031003, 13:41  #10 
Cranksta Rap Ayatollah
Jul 2003
641 Posts 
My knowledge of quantum computers is pretty small, but does the computation time increase for factoring larger numbers?

20031003, 15:45  #11  
Bamboozled!
"πΊππ·π·π"
May 2003
Down not across
2A1E_{16} Posts 
Quote:
I think it is likely to be a long time before we can factor general integers the size of C5. As far as I am aware, the record still stands at 15 for a factorization by a QC. Paul 

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