PrimeGrid’s
The Riesel Problem
On 10 October 2013, 22:01:17 UTC, PrimeGrid’s The Riesel Problem project
eliminated k=304207 by finding the mega prime:304207*26643565-1
The prime is 1,999,918 digits long and will enter Chris Caldwell's “The Largest Known
Primes Database” (http://primes.utm.edu/primes) ranked 23rd overall. This is
PrimeGrid's 11th elimination. 53 k's now remain.
The discovery was made by Randy Ready of the United States using an Intel(R)Xeon(R) CPU X5570 @ 2.93GHz with 24 GB RAM running Windows Server 2003.
This computer took 37 hours 36 minutes to complete the primality test using LLR.
Randy is a member of the Aggie the Pew Team.
Credits for the discovery are as follows:
1. Randy Ready (United States), discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. LLR, primality program developed by Jean Penne
Entry in “The Largest Know Primes Database” can be found here:
http://primes.utm.edu/primes/page.php?id=115875
Hans Ivar Riesel, a Swedish mathematician, showed in 1956 that there are an infinite
number of positive odd integer k's such that k*2^n-1 is composite (not prime) for every
integer n>=1. These numbers are now called Riesel numbers. He further showed thatk=509203 was such one.
It is conjectured that 509203 is the smallest Riesel number. The Riesel Problem
consists in determining that 509203 is the smallest Riesel number. To show that it isthe smallest, a prime of the form k*2^n-1 must be found for each of the positive integer
k's less than 509203. For more information about The Riesel Problem, please visit
Wilfrid Keller's The Riesel Problem: Definition and Status(http://www.prothsearch.net/rieselprob.html).
Using a single PC would have taken years to find this prime. So this timely discovery
would not have been possible without the hundreds of volunteers who contributed theirspare CPU cycles. A special thanks to everyone who offered their advice and/or
computing power to the search - especially Sean Faith and Brian Carpenter who
provided support information from the previous Riesel Sieve effort.
The Riesel Problem project will continue to seek primes for the 53 remaining k's. To
join the search please visit PrimeGrid: http://www.primegrid.com

PrimeGrid’s
The Riesel Problem
About PrimeGrid
PrimeGrid is a distributed computing project, developed by Rytis Slatkevičius, Lennart
Vogel, and John Blazek, which utilizes BOINC and PRPNet to search for primes.
PrimeGrid's primary goal is to bring the excitement of prime finding to the "everyday"
computer user. Simply download the software and let your computer do the rest.
Participants can choose from a variety of prime forms to search. With a little patience,
you may find a large or even record breaking prime.
BOINCThe Berkeley Open Infrastructure for Network Computing (BOINC) is a software
platform for distributed computing using volunteered computer resources. It
allows users to participate in multiple distributed computing projects through asingle program. Currently BOINC is being developed by a team based at theUniversity of California, Berkeley led by David Anderson.
This platform currently supports projects from biology to math to astronomy. For
more information, please visit BOINC: http://boinc.berkeley.edu
PRPNet
PRPNet is a client/server application written by Mark Rodenkirch that isspecifically designed to help find prime numbers of various forms. It is easily
ported between various OS/hardware combinations. PRPNet does not run each
PRP test itself, but relies on helper programs, such as LLR, PFGW, phrot, wwww,and genefer to do the work.
For more information, please visit PrimeGrid’s PRPNet forum thread:
http://www.primegrid.com/forum_thread.php?id=1215
For more information about PrimeGrid and a complete list of available prime search
projects, please visit: http://www.primegrid.com