Riesel Primes k*2^n-1, k<300 [Was "k=1"]

[marc]

Taking 245

[Kosmaj]

No new primes found.

k=7, checked to 1000000 (1M)! Sieving to 1.3M
k=13, checked to 927000, in progress
k=53, checked to 416000, in progress
k=77, checked to 290000, in progress
k=79, checked to 300000, stopped
k=89, checked to 300000, stopped.

Next I'd like to reserve k=21 from n=500000 forward.

It's a disappointment that neither k=7 nor k=13 produced any large primes Next, I'll try k=21 but it is much "denser", about 48 candidates per 1000 n's (after sieving to 1.1 trillion) more than k=7 and k=13 combined.

[Harvey563]

k=25 is checked to 397383, no new primes, continuing to 400000.
k=27 is checked to 488150, no new primes, continuing to 500000.
k=31 is checked to 493000, no new primes, continuing to 500000.
k=57 is checked 200000 to 208000, no new primes, continuing to 210000.
k=59 is reserved 200000 to 210000.
k=61 is reserved 200000 to 210000.
k=71 is checked to 210000, prime for 202642, quitting.
k=83 is checked 200000 to 210000, quitting.
k=85 is checked 200000 to 210000, quitting.
k=87 is checked 200000 to 208500, no new primes, continuing to 210000.
k=173 is checked to 200000, no new primes, quitting.
reserving 175 to 200000.

Harvey563

[Thomas11]

k=11 is checked to n=600000, continuing.
k=29 is checked to n=900000, continuing.

No new primes (yet).

[Harvey563]

k=25 is checked to 400000, no new primes, quitting.
k=27 is checked to 500000, no new primes, quitting.
k=31 is checked to 494600, no new primes, continuing to 500000.
k=57 is checked 200000 to 210000, no new primes, quitting.
k=59 is checked 200000 to 210000, no new primes, quitting.
k=61 is checked 200000 to 210000, no new primes, quitting.
k=87 is checked 200000 to 210000, no new primes, quitting.
k=175 is checked from 90672 to 200000, prime for 143691.
reserving 177 & 189 to 200000.

Harvey563

[Harvey563]

correction: k=175 was checked from 133559 to 200000.

Harvey563

[Templus]

Back from my vacation

reserving k=241, using the new LLR-P4

[Kosmaj]

Finally a prime of a decent size

21*2^538657-1 is prime! 162154 digits

Found using the new LLR-P4. k=21 is completely checked only to n=515000 since some candidates in the 515-518k range are being checked now by another machine.

[Harvey563]

k=177 is checked from 70752 to 200000, primes: 96978, 98353.
k=189 is checked from 73401 to 200000, prime: 175901.

Harvey563

[Templus]

@ Harvey563

I already checked k=177 until n=125k before I went on my holidays and found the same primes as you did. So thank you for double checking

status-report on k=241 , checked to n=168k , no new primes found YET

[Harvey563]

I'm taking k=185 to 200000.

Harvey563