20070318, 00:24  #1 
"Jason Goatcher"
Mar 2005
5·701 Posts 
Looking for a sieving program
Is there a program out there, where you can enter a range of numbers, and it will tell you any factors below a million, a billion, or...?
Mind you, these aren't special form numbers, these are sequential numbers. 
20070318, 02:16  #2  
"Mike"
Aug 2002
1D89_{16} Posts 
Quote:
Code:
for i in `seq 2 10000`; do factor $i; done When we say it ain't fast, we aren't joking. You could factor these by hand faster. Or something. 

20070318, 14:34  #3 
"Mike"
Aug 2002
16611_{8} Posts 
In case you want to list the primes, here is a very ugly BASH program.
Code:
cat file  cut d ':' f 2  sed 's/^ //'  grep v ' ' 
20070318, 20:39  #4 
"Jason Goatcher"
Mar 2005
5·701 Posts 
Since there doesn't seem to be a program that fits my needs, I guess I might as well reveal what I wanted to do. I wanted to find the lowest 114digit number with two brilliant factors. A brilliant number is a number where all the prime factors have the same number of digits. So far, digits 1 through 113 are spoken for.

20070319, 01:14  #5  
"Mike"
Aug 2002
7,561 Posts 
Quote:


20070319, 02:50  #6 
"Richard B. Woods"
Aug 2002
Wisconsin USA
1111000001100_{2} Posts 
jasong's original posting contained no hint, misleading or otherwise, about the size of numbers he sought to factor. His mention of "factors below a million, a billion, or..." hints only at size of possible factors, not of the numbers to be factored.
Last fiddled with by cheesehead on 20070319 at 02:53 
20070319, 03:09  #7 
"Mike"
Aug 2002
7,561 Posts 
Stop making sense. It hurts us so.
The rock and pool Is nice and cool So juicy sweet Our only wish To catch a fish So juicy sweet 
20070319, 17:33  #8 
"Mike"
Aug 2002
7,561 Posts 
Why? Because we were bored.
How long did it take? You don't want to know. Was it pointless? Of course! 
20070319, 19:22  #9  
Bamboozled!
May 2003
Down not across
2·3·41^{2} Posts 
Quote:
First off, write a simple program (yes, write it for yourself  if you can't write it you're not going to succeed in everything else that's needed) which divide all numbers between (say 100^113 and 10^113+1000000) by small primes  those under 1000 say. Anything which isn't divisible by one of those, you write to a file. There are any number of programming languages which will let you do this first stage. If you're on a MS operating system, UBASIC is as good as any and better than most. Then, once you've found all the numbers of interest without any small factors, get hold of an ECM program and use it to find medium size factors of those. GMPECM is the most effecient I know of and it's been ported to many operating systems. Keep using ECM, with ever larger B1 limit, until you get bored. Every time you find a factor of an integer N, remove it from your list. After that phase is over  it will probably take you only a month or so unless you've serious amount of computation available  get hold of a NFS factoring package and use it to do each of the remaining candidates in order of size. Sooner or later you will find a brilliant number. Beware: it took me about 5 years to find the smallest 150brilliant number. Good luck! Paul 

20070319, 19:30  #10  
"Mike"
Aug 2002
7,561 Posts 
Quote:
And he was happy to have it! 

20070319, 21:55  #11  
Jun 2003
1,553 Posts 
Quote:


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