On August 1, 2009, Magnum Bergman (working with PrimeGrid) found the largest known Cullen prime, 6679881*2^6679881+1
On April 20, 2009, Dennis R. Gesker (working with PrimeGrid) found the largest known Cullen prime, 6328548*2^6328548+1
Cullen Primes are Cullen numbers that are prime and of the form Cn = n · 2n + 1 .
Cn is prime for n = 1, 141, 4713, 5795, 6611, 18496, 32292, 32469, 59656, 90825, 262419, 361275, 481899, 1354828, 6328548 and for no other n < 10,000,000; Chris Caldwell maintains the top 20 Cullen Page.
A list of contributors to the Cullen project is here.
PrimeGrid is coordinating a distributed search for Cullen primes using BOINC.
To search for Cullen Primes of other bases, check out Günter Löh's Generalized Cullen Search for 3 ≤ b ≤ 100 and Daniel Hermle's Generalized Cullen Search for 101 ≤ b ≤ 200.
Woodall numbers (Wn = n · 2n − 1) are related to Cullen numbers and are sometimes called Cullen numbers of the second kind. Check here for the Woodall prime search.
If you have any questions about the Cullen Search, you can e-mail Mark Rodenkirch or Ray Ballinger
URL: http://www.prothsearch.net/cullen.html