About a year ago, I had a reproducible error similar to this while
trying to do P-1 factoring on M262143.  I had added a list of all the
known (to me) factors of M262143 to the lowm.txt file, and they
apparently were ok because errors in this file are typically caught when
the factoring is started.
I tried a variety of P-1 limits, but the result at the end of stage 1
was always the same: ERROR: factor doesn't divide N!  I also tried ECM
factoring on the same number with the same error message result. 
Although I had encountered this error message a couple of times before
whle doing ECM factoring on P66536, those errors were NOT reproducible:
when I reran the program on the same seed, the program always ran ok to
the end.

In case anyone else wants to try this, here is my list of factors from
the lowm.txt file:

M( 262143 )C: 7
M( 262143 )C: 7
M( 262143 )C: 73
M( 262143 )C: 127
M( 262143 )C: 337
M( 262143 )C: 439
M( 262143 )C: 3943
M( 262143 )C: 9199
M( 262143 )C: 24967
M( 262143 )C: 28729
M( 262143 )C: 36793
M( 262143 )C: 57457
M( 262143 )C: 262657
M( 262143 )C: 524287
M( 262143 )C: 1560007
M( 262143 )C: 2298041
M( 262143 )C: 8912863
M( 262143 )C: 15212471
M( 262143 )C: 30583351
M( 262143 )C: 54985393
M( 262143 )C: 302587921
M( 262143 )C: 1371458593
M( 262143 )C: 1380150703
M( 262143 )C: 10178663167
M( 262143 )C: 15382298807
M( 262143 )C: 27265714183
M( 262143 )C: 35473416481
M( 262143 )C: 47659091257
M( 262143 )C: 121323854647
M( 262143 )C: 520853887919
M( 262143 )C: 9361973132609
M( 262143 )C: 34088027693833
M( 262143 )C: 130066754524687
M( 262143 )C: 1406791071629857
M( 262143 )C: 2237717449946593
M( 262143 )C: 5271393791658529
M( 262143 )C: 671165898617413417
M( 262143 )C: 2762194134676763431
M( 262143 )C: 7032960672473811601
M( 262143 )C: 4815314615204347717321
M( 262143 )C: 207617485544258392970753527
M( 262143 )C: 42185927552983763147431373719
M( 262143 )C: 17140907466568806171723281481130659780805681
M( 262143 )C: 57037483740488228809445031801958262436578074081
M( 262143 )C: 29724614739876344125010817433703775877960388838436140673
M( 262143 )C: 61641347592475860688686002670152525762503468748858717047
M( 262143 )C:
144780974187086260903935034761413745643636578290924150417
M( 262143 )C:
20712014126148022558481993313919624102421323341432158275969
M( 262143 )C:
2537599745025519134156761164267591913521835535529224725592538658153


Phil Moore

------------------------------

Date: Fri, 24 May 2002 11:30:40 -0400
From: Jud McCranie <[EMAIL PROTECTED]>
Subject: Mersenne: error result

I've been in GIMPS since before the first one was discovered.  Today I

finished an exponent, and saw some stuff I haven't seen before.

After it completed, it said
M14776187 stage 1 complete ---transformations --- time
starting stage 1 GCD
stage 1 GCD complete
ERROR: factor doesn't divide N!
contacting server
etc.

What went wrong?

It looks like at the end of the L-L test, it did a GCD, thought it
found a 
factor, but it wasn't a factor.

For a while during this exponent, I had quick user switching on with 
WinXP.  When I realized that prime95 was running twice as slow, I
figured 
out that quick switching was causing two copies of primr95 to run. 
Could 
that cause a problem?


+---------------------------------------------------------+
|       Jud McCranie                                      |
|                                                         |
| Programming Achieved with Structure, Clarity, And Logic |
+---------------------------------------------------------+



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