Selecting M

199 for a test run that would require stage 2 in P-1; 10 separate 1-curve B1=50000, B2=4000000 runs, succeeded in 7 of 10:

Code:

ECM found a factor in curve #1, stage #1
Sigma=5162481759413312, M199 has a factor: 164504919713
Cofactor is a probable prime!
ECM found a factor in curve #1, stage #1
Sigma=5912327664438779, M199 has a factor: 164504919713
Cofactor is a probable prime!
M199 completed 1 ECM curve
ECM found a factor in curve #1, stage #2
Sigma=7974985130155996, M199 has a factor: 164504919713
ECM found a factor in curve #1, stage #2
Sigma=8865572054271244, M199 has a factor: 164504919713
ECM found a factor in curve #1, stage #1
Sigma=608224716041860, M199 has a factor: 164504919713
Cofactor is a probable prime!
ECM found a factor in curve #1, stage #2
Sigma=1498813620767224, M199 has a factor: 164504919713
M199 completed 1 ECM curve
M199 completed 1 ECM curve
ECM found a factor in curve #1, stage #2
Sigma=4311317535291977, M199 has a factor: 164504919713

(This factor is only 37 bits so would have been found in the recommended 40-44 bits TF.)

Or M

257, B1=120000, B2=4000000, 10 separate curves run individually, of which two found the 49 bit factor that would not be found by recommended level TF (to 40-44 bits):

Code:

ECM found a factor in curve #1, stage #2
Sigma=5976369241598935, M257 has a factor: 535006138814359
M257 completed 1 ECM curve
ECM found a factor in curve #1, stage #2
Sigma=8788874036099382, M257 has a factor: 535006138814359
M257 completed 1 ECM curve
M257 completed 1 ECM curve
M257 completed 1 ECM curve
M257 completed 1 ECM curve
M257 completed 1 ECM curve
M257 completed 1 ECM curve
M257 completed 1 ECM curve