Gratuitous factors thread

[LaurV]

Nice. I have never seen one of my own. In fact, I didn't see a 3-way split for quite a long time either. But I don't work so large composites as you guys.

[charybdis]

A rather lucky ECM factor from aliquot sequence 2360:

Using B1=11000000, B2=35133391030, polynomial Dickson(12), sigma=1:2026970909
Step 1 took 12373ms
Step 2 took 5994ms
********** Factor found in step 2: 8640369870909863595929431692681480218474037077400129286983763
Found prime factor of 61 digits: 8640369870909863595929431692681480218474037077400129286983763
Prime cofactor 129269788173717510352741587971842512872817913474983535163294531334491305593503434770571399 has 90 digits

[Batalov]

Hey, cool, must be a good,lucky day for factors. I also just got an uncharacteristically large hit (for seq 2081190):

> cat EC.44
GMP-ECM 7.0.3 [configured with GMP 6.1.1, --enable-asm-redc] [ECM]
Input number is 26659319056687683461054149321917986804957358719605281966548936444886896624104353412491288953593160598080321001018543288026127232842327373237 (140 digits)
Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=1:3707545622
Step 1 took 182540ms
Step 2 took 55670ms
Run 2 out of 200:
...
Run 5 out of 200:
Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=1:3798568687
Step 1 took 182177ms
********** Factor found in step 1: 32756224828930142289475723150116220166815023466048767025627
Found prime factor of 59 digits: 32756224828930142289475723150116220166815023466048767025627
Prime cofactor 813870316128197392584899168196680294640704883649117820738362327353816069049664431 has 81 digits

[Brownfox]

Yup, today is officially Large Factor day:

GMP-ECM 7.0-dev [configured with MPIR 2.6.0, --enable-openmp] [ECM]
Input number is 19665584029300424610206656998744724640118849009115415651634333787794657657987385775417086739192039189614555026416812029751027390818218736070170758482564486193541449884496154967983274557938323133 (194 digits)
...
Run 89 out of 1033:
Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=1:3631092842
Step 1 took 758234ms
Step 2 took 198812ms
********** Factor found in step 2: 14206140704026661221619235881597509147461207215069425801
Found probable prime factor of 56 digits: 14206140704026661221619235881597509147461207215069425801
Probable prime cofactor 1384301650885825087848187760503761406631430275388925914731703001560119263184362769750089653715830933780189618374942258401954949617045411733 has 139 digits

[kruoli]

Originally Posted by Batalov

I also just got an uncharacteristically large hit (for seq 2081190): [...]

A group order of \(2^3 \cdot 269 \cdot 8{,}807 \cdot 32{,}887 \cdot 48{,}017 \cdot 50{,}341 \cdot 59{,}791 \cdot 137{,}251 \cdot 1{,}251{,}461 \cdot 4{,}406{,}351 \cdot 18{,}528{,}707 \cdot 25{,}929{,}229\), wow!

[sean]

New personal best ...

GMP-ECM 6.4 [configured with GMP 6.0.0, --enable-asm-redc] [ECM]
Input number is (177!+1)/1891548004136643904823/271 (299 digits)
Using B1=110000000, B2=776278396540, polynomial Dickson(30), sigma=1450894984
Step 1 took 1259302ms
Step 2 took 246545ms
********** Factor found in step 2: 107357044729767130172699954387081510561518701754865074363224611 
Found probable prime factor of 63 digits: 107357044729767130172699954387081510561518701754865074363224611 
Composite cofactor ((177!+1)/1891548004136643904823/271)/107357044729767130172699954387081510561518701754865074363224611 has 237 digits

sadly still a long way off the pace for the current top 10.