[URL="http://www.mersenne.org/M15773"]M15773[/URL] has a factor: [URL="http://www.mersenne.ca/factor/17579521249732269431622694421369772823"]17579521249732269431622694421369772823[/URL].
38 digits, 123.725 bits.
Found in stage 2 of ECM with B1 = 1,000,000 and B2 = 100,000,000.
[$]k = 3^2 \cdot 1508475559895261 \cdot 41047050622854043[/$]

[QUOTE=kruoli;479327][URL="http://www.mersenne.org/M15773"]M15773[/URL] has a factor: [URL="http://www.mersenne.ca/factor/17579521249732269431622694421369772823"]17579521249732269431622694421369772823[/URL].
38 digits, 123.725 bits.
Found in stage 2 of ECM with B1 = 1,000,000 and B2 = 100,000,000.
[$]k = 3^2 \cdot 1508475559895261 \cdot 41047050622854043[/$][/QUOTE]

Can you check your logs for the sigma for that particular ECM curve? That will tell us the group order (the generalized analog to k in P-1 method, the part that needs to be smoother than the bounds).

Sure! Here it is: [$]\sigma = 831178265486145[/$]. If I'm not mistaken, group order is [$$]17579521249732269439175142576334117224 = 2^3 \cdot 3^4 \cdot 61^2 \cdot 71 \cdot 137 \cdot 173 \cdot 883 \cdot 9209 \cdot 44909 \cdot 414559 \cdot 28618999[/$$]

Is recording the sigma useful in general? Primenet doesn't store it. Should it?

FactorDB lets you report it. Is it worth going through old results.txt files and reporting B1, B2, sigma for factors of a certain size for sufficiently small exponents?

For example, back in October and November 2016 I found

M5479 has a factor: 13557556381615196797243034050392909446329
Sigma=7054537469636144, B1=3000000, B2=300000000
order = 13557556381615196797212833579170371231744 = 2^13 · 3^2 · 7 · 71 · 29587 · 48859 · 126457 · 742673 · 787907 · 3458849

M5849 has a factor: 6122074172317059755884428199928856623
Sigma=3773616030419932, B1=3000000, B2=300000000
order = 6122074172317059756386103969515680128 = 2^7 · 3 · 17 · 271^2 · 653 · 626117 · 1229269 · 2347777 · 10821997

M6317 has a factor: 4012681826290985504902063790032196593
Sigma=7077307037954735, B1=3000000, B2=300000000
order = 4012681826290985506009411978310188020 = 2^2 · 3^2 · 5 · 251 · 12541 · 77747 · 302663 · 389651 · 787601 · 980689

I reported the sigmas to FactorDB just now.

There are various others. What are the criteria for noteworthiness?

Two interesting P-1 finds today, both exponents had 200+ ECM curves with B1=50,000 and previous P-1 (B1=2e6 B2=20e6 E=12)

Found with B1=10e6 , B2 =200e6 E=12)

[URL]http://www.mersenne.ca/exponent/1618957[/URL]
33digits, 109bits
k=193635371239965998637830543 = 7 × 29 × 761 × 1129 × 58787 × 130729 × 144463063

[URL]http://www.mersenne.ca/exponent/1619249[/URL]
25digits, 81bits
k=597596506944850360 = 23 × 5 × 7727 × 81043 × 23857319

[QUOTE=VictordeHolland;479457]
k=597596506944850360 =23 × 5 × 7727 × 81043 × 23857319[/QUOTE]
Copy past mistake, it should be:
2[B]^3[/B] × 5 × 7727 × 81043 × 23857319

P-1 found a factor in stage #1, B1=675000.
UID: Jwb52z/Clay, M85843097 has a factor: 1359449597493721279537921 (P-1, B1=675000)

80.169 bits.

Hi,

not a big factor... but a smooth one:
P-1 found a factor in stage #1, B1=695,000.
M85,872,673 has a factor: 132,249,907,283,167,396,650,217 (76.80 Bits; k = 770,034,882,244,596 = 2[SUP]2[/SUP] * 3 * 19[SUP]2[/SUP] * 31 * 101 * 157 * 431 * 839)

Oliver

Yay, four 100bits+ factors in a couple of days

[code]
ECM found a factor in curve #26, stage #2
Sigma=6601270117148099, B1=50000, B2=5000000.
M1645829 has a factor: 4926163898475197542012571417906273 (ECM curve 26, B1=50000, B2=5000000)[/code]k = 1496560061365791203707241584 = 2^4 × 366327723677 × 255331490875187
34 digits (112 bits)
Lucky to find it with those bounds and only after 26 curves :)

[code]
ECM found a factor in curve #189, stage #1
Sigma=8480282508537123, B1=50000, B2=5000000.
M1646017 has a factor: 1508150793506270218417297 (ECM curve 189, B1=50000, B2=5000000)[/code]k = 671925754144305528132925 = 5^2 × 11 × 2262149 × 1080108506869603
31 digits (101 bits)
Pretty nice also

[code]
P-1 found a factor in stage #2, B1=10000000, B2=200000000, E=12.
M1635061 has a factor: 35277055408841049507268416482009 (P-1, B1=10000000, B2=200000000, E=12)[/code]k = 10787687862667218381231164 = 2^2 × 7 × 67 × 337 × 102107 × 3815521 × 43798201
32 digits (105 bits)

[code]
P-1 found a factor in stage #2, B1=10000000, B2=200000000, E=12.
M1632031 has a factor: 5765639839704486562062940217495923385660941630658516500657 (P-1, B1=10000000, B2=200000000, E=12)[/code]Too bad it is composite:
3653580423682983757805163337 and 1578079355344379124902894328361
but still 28 digits (92 bits) and 31 digits (101 bits)

Victor out.

89 bits & 75 bits
 

ECM found a factor in curve #2, stage #2
Sigma=4638489409098898, B1=50000, B2=5000000.
UID: nitro/haswell, M2363233 has a factor: 653802529177774532317345711 (ECM curve 2, B1=50000, B2=5000000), AID: AAD7ED003888C5890508D85DF6B13096

ECM found a factor in curve #1, stage #2
Sigma=4290627876618080, B1=50000, B2=5000000.
UID: nitro/haswell, M2350331 has a factor: 62772178479336230190607 (ECM curve 1, B1=50000, B2=5000000), AID: 02EDEEAFE3CDC8C4486449D27CFCA701

Exponent and factor both end in 6 and 3
 

56663333 Factored 117668043758277867795710633