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Old 2010-08-31, 19:58   #210
wblipp
 
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The low base Brent composite 43^149-1 had 2 previously known factors of 9 and 11 digits. The remaining C224 was factored as P59 * P165.

ECM to t50 by yoyo@home
SNFS sieving by RSALS
Post Processing by Carlos Pinho
Code:
49^149-1

P59: 86959139755992334146951905688612930845160757695048012660011
P165: 210379001213136221541664472540640112042495029485679467795377614362692978042544981962987197932691344997299555981733468380709579937416527275299320760668948931886000961
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Old 2010-09-03, 14:23   #211
warut
 
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Default 5^1024+1024^5

The loveliest factorization I ever found was that of 5^1024+1024^5. It required a lot of luck and very little factoring effort.

5^1024+1024^5 = 113 * 809 * 160313 * 42387041 * 7329030409 * 425520498209 * 3024735158536046561 * P324 * P335
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Old 2010-09-03, 15:04   #212
R.D. Silverman
 
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Quote:
Originally Posted by warut View Post
The loveliest factorization I ever found was that of 5^1024+1024^5. It required a lot of luck and very little factoring effort.

5^1024+1024^5 = 113 * 809 * 160313 * 42387041 * 7329030409 * 425520498209 * 3024735158536046561 * P324 * P335
Please explain. Is there an algebraic factorization here that I am missing?
This is far beyond current capabilities otherwise.
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Old 2010-09-03, 17:57   #213
warut
 
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Quote:
Originally Posted by R.D. Silverman View Post
Please explain. Is there an algebraic factorization here that I am missing?
This is far beyond current capabilities otherwise.
Yes, it admits an algebraic factorization because
5^1024 + 1024^5 = (5^256)^4 + 4*(2^12)^4.
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Old 2010-09-03, 21:20   #214
R.D. Silverman
 
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Quote:
Originally Posted by warut View Post
Yes, it admits an algebraic factorization because
5^1024 + 1024^5 = (5^256)^4 + 4*(2^12)^4.
Yes. Nice result.
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Old 2010-09-05, 02:41   #215
apocalypse
 
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643945470136695841369 | M52272617

Found with P-1 where k = 2^2 * 3 * 17 * 31 * 499 * 709 * 2753

Man, that is smooth.
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Old 2010-09-08, 07:51   #216
xilman
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Nothing too unusual about a p49 these days but this one was found by gmp-ecm using a B1 value of 1M, which is optimal for factors 14 digits smaller.

Code:
[2010-09-07 11:15:27 GMT] GC_5_691_C421: probable factor returned by pcl@maat (maat4)!  Factor=2341673831256161998097409059802772958624071425517  Method=ECM  B1=1000000  Sigma=1067295280
GC_5_691 is 691*5^691+1

Paul
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Old 2010-09-15, 12:16   #217
R.D. Silverman
 
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Default Top 10?

Why hasn't Blair Kelly's P64 factor of L1956 shown up on the
ECM Top 10 page?
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Old 2010-09-30, 17:31   #218
fivemack
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5748 index 1368:
Code:
Thu Sep 30 17:37:00 2010  prp69 factor: 674788222835164103353823038231553835542017738166824174868830262813749
Thu Sep 30 17:37:00 2010  prp86 factor: 28250192298752567946214115957812098958537842561773991296565797999910836802368478096257
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Old 2010-10-11, 21:40   #219
wblipp
 
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The Brent composite 541^89-1 had 3 previously known factors of 3, 6, and 11 digits. The remaining C223 has been factored as P89 * P135.

ECM to t50 by yoyo@home
SNFS sieving by RSALS
Post Processing by ZetaFlux
Code:
541^89-1

P89: 22258230882835545380142293457243394259854811189356144633053908389611484579705336039818299
P135: 156308318050822004478554684741294957177596514375932813652522859001742185442920716992906314508709642460414410563253635690990135902349719
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Old 2010-10-15, 09:02   #220
Batalov
 
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Talking a factor of 220 digits...

> echo "(10^9270-1)/3^4/7" | ecm 5e4
Input number is (10^9270-1)/3^4/7 (9268 digits)
Using B1=50000, B2=15446350, polynomial x^2, sigma=3682263502
Step 1 took 99069ms
********** Factor found in step 1: 9573726981993820200551709701677247363792903115583020462044881149461982541836124423370428786937847788404630054782651343281856841362377745746844353951111544591359795066465415084994921961147188454685295861838434800628490443
Found composite factor of 220 digits: 9573726981993820200551709701677247363792903115583020462044881149461982541836124423370428786937847788404630054782651343281856841362377745746844353951111544591359795066465415084994921961147188454685295861838434800628490443
Composite cofactor ((10^9270-1)/3^4/7)/9573726981993820200551709701677247363792903115583020462044881149461982541836124423370428786937847788404630054782651343281856841362377745746844353951111544591359795066465415084994921961147188454685295861838434800628490443 has 9048 digits


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