I sieved up to 700bn and only had 840 candidates per 100k. Along with
that low # of candidates per thousand is a low # of primes. The risk
of a really low-weight k like this is that you won't find *any* primes.
To find the low-weight k's for k<300, I sieved n=0-10k up to 100M.
Below is the number of candidates left, # of primes in n=0-5k, and K

[CODE]
Weight Primes K
186 7 283
185 6 269
178 7 101
176 4 29
169 6 221
146 4 251
145 8 223
130 2 239
117 3 191
116 3 127
107 5 247
53 3 253
[/CODE]

For comparison, K=25 had 582 candidates left and 21 primes. The highest
weight was K=195 with 1466 candidates and 37 primes.

From test your own k:

5169615*2^294163-1 (88559 digits)

From choose your own k - the 5th reported prime for this k
22932195*2^313832-1 (94481 digits)

Megabit
 

My first megabit prime :w00t: :cool: :banana:

[B]77*2^1467554-1[/B] (441780 digits)

After realizing that k=77 is a promising multiplier, and finding the primes at 607k (in December 2004) and 855k (in June last year) I decided to test megabit candidates working from 1M forward and from 1.5M backward. It was a time consuming "operation" but it payed off!

WTG, very nice

:w00t: Great prime Kosmaj! :bow:

Grobie and Cruelty, thanks!

Here is one more big one :w00t: :shock:
[B]2995125705*2^891645-1[/B] (268422 digits)

This one eluded us for quite a while! And it closely matches Larry's forecast (890k) based on previous largest gap.

Great primes Kosmaj!

This is the new largest gap. Duplicating the largest gap would have put this prime at n=891578!

BTW, this puts our project score ahead of 15k already. Now #3 in primes
and #10 in score.

80555475*2^281095-1 (84626 digits)

1222853775*2^249279-1 (75050 digits)