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Old 2018-08-17, 13:19   #452
Nooks
 
Jul 2018

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ECM on a C213, the last divisor of (34*10^229-61)/9 with sigma=1:3941682105:

Using B1=2900000000, B2=82640965106716, polynomial Dickson(30), sigma=1:3941682105
[...]
********** Factor found in step 2: 35020442769329876367522852735060830348867981850170604303099578467
Found prime factor of 65 digits: 35020442769329876367522852735060830348867981850170604303099578467
Prime cofactor 6463948784722816185901384621852688761921664616020783901443547268726228461664676485561963639543974467240297445194995726733180417921657435498535243769 has 148 digits

The factor was found on the 25th curve; taking into account all the other cores running curves this was the 2400th curve of only 9600 I planned to run before handing the problem to CADO-NFS, so I'm counting myself quite lucky!
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Old 2018-08-17, 13:49   #453
ET_
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Quote:
Originally Posted by Nooks View Post
ECM on a C213, the last divisor of (34*10^229-61)/9 with sigma=1:3941682105:

Using B1=2900000000, B2=82640965106716, polynomial Dickson(30), sigma=1:3941682105
[...]
********** Factor found in step 2: 35020442769329876367522852735060830348867981850170604303099578467
Found prime factor of 65 digits: 35020442769329876367522852735060830348867981850170604303099578467
Prime cofactor 6463948784722816185901384621852688761921664616020783901443547268726228461664676485561963639543974467240297445194995726733180417921657435498535243769 has 148 digits

The factor was found on the 25th curve; taking into account all the other cores running curves this was the 2400th curve of only 9600 I planned to run before handing the problem to CADO-NFS, so I'm counting myself quite lucky!
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Old 2018-08-18, 19:49   #454
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Code:
Input number is (109^123-1)/(109^41-1)/95898591887152691733740679 (142 digits)
Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=1:3742107819
Step 1 took 66545ms
Step 2 took 23004ms
********** Factor found in step 2: 113910660004153337924628664386678247208828533
Found prime factor of 45 digits: 113910660004153337924628664386678247208828533
Prime cofactor ((109^123-1)/(109^41-1)/95898591887152691733740679)/113910660004153337924628664386678247208828533 has 98 digits
This factor appeared on curve 92 out of a planned 4000.
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Old 2018-09-16, 17:54   #455
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C135 from 1208^47+1:

Code:
prp43 = 7872050983542095687417246190511880248639711
prp92 = 16940363046999582482928413622346911064605327855533940683539949731286830685125532654826597073
C125 from 1259^47+1

Code:
prp38 = 98345853344307565253324824092518095601
prp87 = 929528781257601652853545435226628885326214271769204819819291780270828421426874911996487
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Old 2018-12-10, 13:54   #456
fivemack
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Default L3780 factored

199-digit GNFS, done entirely locally

Code:
N 1253697014483921701519774710080293856978446067093422585355224278757029355514329819946916985971979863264272814638205843444068083099253312799641803553719988196912895006268194994880801257942554688556001
SKEW 127028183.52
A0 -595638964036345481237071140491743854143245809544
A1 29926818433789606747718647951662435504208
A2 307924512754708078991927303315680
A3 -4781679268252586458599169
A4 -22400530233973836
A5 102927636
R0 -104023657306189391164144906961130612015
R1 651664577069232468431
Sieved Q=30M .. 285M and 330M..335M with gnfs-lasieve4I16e; 12 Aug - 10 Nov on 64 cores E5-2650 and some other resources; linear algebra was 27 days on 14 cores i9-7940X

Code:
lpbr: 33
lpba: 33
mfbr: 66
mfba: 96
alambda: 3.5
rlambda: 2.4
alim: 268000000
rlim: 268000000
Code:
Tue Nov 13 07:30:38 2018  matrix is 48788680 x 48788857 (23378.5 MB) with weight 7047295017 (144.44/col)
Tue Nov 13 07:30:38 2018  sparse part has weight 5543070617 (113.61/col)
Tue Nov 13 07:40:47 2018  filtering completed in 2 passes
Tue Nov 13 07:40:57 2018  matrix is 48786801 x 48786976 (23378.4 MB) with weight 7047214552 (144.45/col)
Tue Nov 13 07:40:57 2018  sparse part has weight 5543053801 (113.62/col)
Tue Nov 13 07:43:08 2018  matrix starts at (0, 0)
Tue Nov 13 07:43:15 2018  matrix is 48786801 x 48786976 (23378.4 MB) with weight 7047214552 (144.45/col)
Tue Nov 13 07:43:15 2018  sparse part has weight 5543053801 (113.62/col)
Tue Nov 13 07:43:15 2018  saving the first 240 matrix rows for later
Tue Nov 13 07:43:27 2018  matrix includes 256 packed rows
Tue Nov 13 07:43:42 2018  matrix is 48786561 x 48786976 (21440.4 MB) with weight 5118664178 (104.92/col)
Tue Nov 13 07:43:42 2018  sparse part has weight 4839889639 (99.20/col)
Tue Nov 13 07:43:42 2018  using block size 8192 and superblock size 473088 for processor cache size 19712 kB
Tue Nov 13 07:45:56 2018  commencing Lanczos iteration (14 threads)
Tue Nov 13 07:45:56 2018  memory use: 29766.8 MB
Tue Nov 13 07:47:23 2018  linear algebra at 0.0%, ETA 637h43m
Tue Nov 13 07:47:47 2018  checkpointing every 80000 dimensions
Mon Dec 10 04:01:57 2018  lanczos halted after 191142 iterations (dim = 48786558)
Mon Dec 10 04:05:48 2018  recovered 29 nontrivial dependencies
Mon Dec 10 04:06:03 2018  BLanczosTime: 2324842
Mon Dec 10 04:06:03 2018  elapsed time 645:47:23
Code:
Mon Dec 10 12:47:23 2018  p82 factor: 9214409416745614101198894993721726856303159042273240016125104117470329343249250561
Mon Dec 10 12:47:23 2018  p117 factor: 136058314513954814229280792975681347764936790375643059794253062274788902853667069820292458749493930656793985621603041

Last fiddled with by fivemack on 2018-12-10 at 14:15
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Old 2019-01-02, 17:36   #457
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59-digit factor of near-repdigit (691*10300-7)/9 was found by ECM

Code:
Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=3032066922
Step 1 took 382110ms
Step 2 took 101223ms
********** Factor found in step 2: 21601138366813705693033870951386003818115059066377541324921
Found probable prime factor of 59 digits: 21601138366813705693033870951386003818115059066377541324921
Composite cofactor 1416732463683710775182530542771135815901595515342842856966117614129678227859411077172659990398292541537568243400899333336769174248499204974915626874899 has 151 digits
Happy New Year everyone!
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Old 2019-01-02, 18:10   #458
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Quote:
Originally Posted by unconnected View Post
59-digit factor of near-repdigit (691*10300-7)/9 was found by ECM

Code:
Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=3032066922
Step 1 took 382110ms
Step 2 took 101223ms
********** Factor found in step 2: 21601138366813705693033870951386003818115059066377541324921
Found probable prime factor of 59 digits: 21601138366813705693033870951386003818115059066377541324921
Composite cofactor 1416732463683710775182530542771135815901595515342842856966117614129678227859411077172659990398292541537568243400899333336769174248499204974915626874899 has 151 digits
Happy New Year everyone!
Possibly the largest of the year so far :)
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Old 2019-01-07, 07:18   #459
VictordeHolland
 
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"Victor de Hollander"
Aug 2011
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Code:
P-1 found a factor in stage #2, B1=2000000, B2=40000000, E=6.
M55715311 has a factor: 7239753241433926010086285741758451306831 (P-1, B1=2000000, B2=40000000, E=6)
40 digit factor, not composite :).
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Old 2019-01-11, 22:48   #460
petrw1
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Default Factored twin primes

https://www.mersenne.org/report_expo...xp_hi=58184849
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Old 2019-01-12, 05:28   #461
LaurV
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not really twins (difference of 10), and generally, you can't factor a prime...
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Old 2019-01-12, 07:05   #462
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Heh. Which sort of reminds me, I kinda shot myself in the foot a week ago. I was LL double checking a few exponents and decided to run TF a bit further just for the heck of it ...and found a factor on one of them. Some CPU time wasted, but more saved, as it wasn't even halfway through at that point.

M51202189

It even had some (old? low bounds?) P-1 work done on it, but then again, mersenne.ca says that min. B1 is 20,857 and min. B2 10,925,329,931 so maybe it was just one of those hard to find factors.
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