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Old 2012-02-22, 06:28   #50
A Sunny Moo
mdettweiler's Avatar
Aug 2007

3·2,083 Posts

Originally Posted by Neo View Post
The server says "14th Drive (K=600-1001, n=1M-2M)"

Below is all -1 primes for 600<K<1001 for N=1M-2M)
This is confusing. ??

RPS didn't start their search at N=1M? for all k 600-1001?

The history of this range is somewhat interesting. Before NPLB began actively searching the range, k=300-1001 was handled by the PrimeSearch project, which provided a web-based automated reservation system for individual k's within the range. Over time the project lapsed into inactivity as it ran into technical difficulties with its website, and much of their later search data ended up being spotty and unreliable. Seeing the inactivity at PrimeSearch, RPS did some limited searches on an individual-k basis, starting from the (assumed correct) PrimeSearch testing limits and somtimes skipping forward to top-5000 ranges. In general, though, the range didn't see much activity during this period, due to uncertainty as to who "owned" the range (so to speak, since of course nobody can "own" a number per se). NPLB was started as an attempt to revitalize the original PrimeSearch effort (it was, in fact, a renaming of the original project with an recognized transfer of leadership from the original admin to Gary), and started right away on the entire continuous k=300-1001, n<1M range. (We completed that goal last year and are now working on completing the entire range to n=2M.)

The idea of doing continuous searches over large blocks of k and n was actually somewhat unique to NPLB when it started--to this day, AFAIK, NPLB and PrimeGrid are the only projects to utilize this approach on a large scale in the Riesel and Proth number spaces. RPS has done some of this recently as well with their 11th Drive on the k=2000-2300 range, though unlike NPLB they opted to start at the current top-5000 threshold level and skip k's that may have (but haven't been confirmed firmly) already tested.

Anyway, long story short, that's how the handful of pre-NPLB primes you found (from 617*2^1175468-1 up on your list) got there--they were found in previous sporadic searches in the range by RPS, pre-NPLB PrimeSearch, and other unaffiliated prime hunters.
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