1. This one isn't as smooth as the one I found earlier this month, but still pretty smooth:

4506302931860941 | 19249*2^10139378+1
4506302931860940 = 2^2*3*5*7*73*199*293*911*2767  Reply With Quote

2. Secondpass...half way through the range on B1=B2=20000. Will up this depending on the rate of double-check tests.

1393019896005342 | 24737*2^4351903+1

(p just over 2^50)

p-1 = 2 * 3^2 * 11 * 167 * 557 * 5399 * 14009  Reply With Quote

3. I got a big one this morning:

104061448755062288629 | 10223*2^3927977+1

BTW, can someone check their logs and tell me how much time a current doublepass PRP takes on a P4. Also let me know the speed of your machine.
Thanks.  Reply With Quote

4. Nice.

n=3870847 took 15 hours on a P4 3.0GHz running Linux
n=3876754 took 15 hours on a 3.0GHz Xeon running Win2k Server.  Reply With Quote

5. Originally posted by garo
104061448755062288629 | 10223*2^3927977+1
p-1 = 2^2 x 3 x 109 x 173 x 643 x 4177 x 6217 x 27541  Reply With Quote

6. Garo,

What's your success rate using the small bounds. And do you think it's worth the effort to P-1 the unfactored ranges? If so I'll start a new thread for those n 4M<n<5M that are previously untested.

At the rate we are proceeding with these doublechecks, ~1K tests per day and less than <21K between 4M<n<5M. I have a feeling we will double check out to at least 5M fairly soon, even if the firstpass que is populated.  Reply With Quote

7. On my 2.6GHz the PRP should be taking about 900*3000/2600 = 1038 min or 17hr 18min. I tried P-1 with Pfactor with sieve depth being the correct 49.7. The lowest factor value for which Prime95 worked was 2.7 which gave me bounds of B1=20k and B2=165K. With these bounds the chance of finding a factor was 0.435 and the test took about 620 seconds. Hence P-1 was saving one test every 2375 minutes.

Hence we can conclude that:

1) P-1 is not worth it. You can do a test in half the time it takes to find a factor.
2) Prime95's calculation is accurate and when it says no point doing P-1 factoring, there really is no point doing P-1 factoring.  Reply With Quote

8. This one is smoother than your average factor:
18628509020177411 | 67607*2^10629251+1
18628509020177410 = 2*5*17*1297*1601*6553*8053  Reply With Quote

9. Not bad HC... not bad at all. The smoothest factor was found by sieve above post.

But yours certainly ranks in the smoothest I've seen for P-1 thus far.  Reply With Quote

10. Originally posted by vjs
Not bad HC... not bad at all. The smoothest factor was found by sieve above post.

But yours certainly ranks in the smoothest I've seen for P-1 thus far.
The smoothest I've found by P-1 is:
268260631411561 | 10223*2^5240741+1
268260631411560=2^3*3*5*101*241*293*463*677

Back in the early days of P-1 mklasson found:
40315798264717 | 21181*2^4031084+1
40315798264716=2^2*3^3*13*211*367*601*617  Reply With Quote

11. Both cool...   Reply With Quote

12. Those are certainly impressive.  Reply With Quote

13. Hurrah, after weeks of nothing from P-1 I finally get one at 6:47am on New Years Day.

7233758839303943 | 24737*2^10645207+1

P-1 = 2 * 11 * 29 * 97 * 271 * 2333 * 184879  Reply With Quote

14. 1058699706255400291 | 33661*2^10649232+1

p-1 = 2 * 3 * 5 * 29 * 193 * 7607 * 28549 * 29033  Reply With Quote

15. Just found with ECM @ 25 digits

6112285295043972389 | 67607*2^7691+1

which was the 4th smallest unfactored n for k=67607   Reply With Quote

16. I'm doing P-1 on 200000 to 250000 but I just submitted these factors:-

110339071626803 | 33661*2^224160+1
4802938257372379 | 55459*2^228718+1
3068443382948634853 | 21181*2^231548+1

without logging in. Should be assigned to user 8141. Ta.  Reply With Quote

17. ECM found a factor in curve #3, stage #2
Sigma=5670788764645674, B1=7400, B2=740000.
10223*2^96221+1 has a factor: 278687290515007924794729914252113

33 digits. And ECM reports it as being prime. Biggest for us this year.   Reply With Quote

18. Originally Posted by MikeH
ECM found a factor in curve #3, stage #2
Sigma=5670788764645674, B1=7400, B2=740000.
10223*2^96221+1 has a factor: 278687290515007924794729914252113

33 digits. And ECM reports it as being prime. Biggest for us this year. Good work but I'm afraid it is composite:-

642379309914469 x 433836031475102077  Reply With Quote

19. Originally Posted by Greenbank
Good work but I'm afraid it is composite:-

642379309914469 x 433836031475102077
Ahh. Must check my ECM settings for primality testing.   Reply With Quote

20. If it's under 2^64 then I use the linux command line program 'factor'.

If it's bigger than 2^64 then I just stick it through Alpetron's applet: http://www.alpertron.com.ar/ECM.HTM  Reply With Quote

21. Thanks for the link. Very useful and interesting.  Reply With Quote

22. 3617343986912807923736443 | 67607*2^202131+1

p-1 = 2 * 3^2 * 71 * 263 * 9209 * 11383 * 90847 * 1130117

B1=1M B2=100M  Reply With Quote

23. you realize that by raising the B1 by 131K yo ucould have found it without performing stage 2  Reply With Quote

24. Originally Posted by Keroberts1
you realize that by raising the B1 by 131K you could have found it without performing stage 2
How much time (percentage) would it have saved?

Which would have been better?
Raising B1 by 131K, or lowering B1/B2 by a factor of 10?  Reply With Quote

25. But how would I have known to do that?

You've got to set bounds without knowing what the factors will look like.  Reply With Quote

26. If I'm not mistaken, Prime95 suggests a B2/B1 ratio of around 20 for B1 values at 1,000,000.  Reply With Quote

27. Yup that's always the point...

One could also say, you could have simply taken the number

67607*2^202131+1

and divided it by

3617343986912807923736443

Seriously though, what were your memory requirements like for the stage2 portion. Also time to complete for each stage, a 1:100 ratio for B1:B2 seems a little high but it works.

Are you doing stage two with prime95 have they married the two clients yet.  Reply With Quote

28. It was a windows box that wasn't networked and that I would only visit once a week or so. So I wanted to give it a big chunk of work without worrying about it, hence the large bounds.  Reply With Quote

29. [Fri Feb 24 07:35:05 2006]
ECM found a factor in curve #80, stage #2
Sigma=4857056233298550, B1=250000, B2=25000000.
33661*2^5112+1 has a factor: 1462205790618779672559199619

28 digits. 6th smallest n for that k. And it realy is prime this time.   Reply With Quote

30. [Sat May 13 01:18:10 2006]
P-1 found a factor in stage #2, B1=70000, B2=822500.
24737*2^11050087+1 has a factor: 594262015630211281

p-1= 2 ^ 4 x 3 x 5 x 11 x 17093 x 54449 x 241861

2^4??

And of course it has to be a composite.  Reply With Quote

31. [Fri Oct 26 22:49:45 2007]
P-1 found a factor in stage #2, B1=130000, B2=2200000.
55459*2^15009238+1 has a factor: 5155366181720738537

and the factor is prime   Reply With Quote

32. [Fri Dec 14 17:07:25 2007]
ECM found a factor in curve #2260, stage #1
Sigma=7131277753749641, B1=3000000, B2=300000000.
10223*2^1181+1 has a factor: 2869295942753555058435842630879466239475749080003

The factor is prime. 49 digits long.  Reply With Quote

33. Wow that is actually quite the find!!! Well done.

Did you check to see if the residual is prime or not? ( nope it's composite) I would say probably not prime but it would be interesting to know.

P-1 = 2 x 3 ^ 2 x 23 x 189661 x 39 361343 990616 327487 x 928 382719 429012 307749
P+1 = 2 ^ 2 x 40037 x 106 442681 x 4 343431 551583 x 38752 974121 352341 178651

Nice....  Reply With Quote

34. 11878266738982198597668979 | 10223*2^39449+1
6650798327357434873224599831 | 10223*2^10757+1
650124655703350600814106133 | 10223*2^15437+1
9419400746144284880591 | 10223*2^41285+1
4380505951119731733855769913 | 10223*2^17477+1
13217355082313000541253 | 10223*2^42797+1

Theres a few more factors that my machine found overnight. They've all been verified and submitted.

On the 49 digit factor I haven't done any tests with the residual other than just testing to see if the factor was prime or not.  Reply With Quote

Page 5 of 5 First 12345

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•