Contribution and Reservation

4·10²³⁷-9 =: 3(9)₂₃₆1_<238>; = 13 · 165953750818291137381672377369_<30> · [1854084684287800831255026300758556765515624934165962534138511682886627257448422049835732162986643665214034880887015096418780059564585634647765688001378107892556545241259313889698967281895113354080477266785803_<208>] (Makoto Kamada / GMP-ECM 6.2.1 B1=250000, sigma=2541232610 for P30 / Nov 3, 2008) SUBMIT/RESERVE

Status

Expression:	4·10²³⁷-9
Composite Factor:	185408468428780083125502630075855676551562493416596253413851 168288662725744842204983573216298664366521403488088701509641 878005956458563464776568800137810789255654524125931388969896 7281895113354080477266785803 (208-digit)
Status:	Not factored. Not reserved. You can submit its factors or reserve it for submitting in the future.

How to factor it

ECM, P-1, P+1

Look for prime factors by GMP-ECM first. Refer to the section "Efforts by ECM". Not only ECM but also P-1/P+1 may be helpful.

SNFS

Use GGNFS and/or Msieve if GMP-ECM cannot find a factor. The SNFS difficulty of this composite number is 237.90-digit and the GNFS difficulty is 207.27-digit. SNFS must be faster than GNFS. It will take about 355 CPU-days to factor this composite number on 64-bit Opteron-2600MHz.

Put factMsieve.pl to which $GGNFS_BIN_PATH and $NUM_CPUS were modified properly in the working directory 39991_237.
Put the following polynomial file 39991_237.poly in there too.
And then, run "perl factMsieve.pl 39991_237".

39991_237.poly ^*1

n: 1854084684287800831255026300758556765515624934165962534138511682886627257448422049835732162986643665214034880887015096418780059564585634647765688001378107892556545241259313889698967281895113354080477266785803
m: 2000000000000000000000000000000000000000
deg: 6
c6: 125
c0: -18
skew: 0.72
type: snfs
lss: 1
rlim: 65000000
alim: 65000000
lpbr: 30
lpba: 30
mfbr: 60
mfba: 60
rlambda: 2.7
alambda: 2.7

*1 These parameters were not fully adjusted. The approximate expressions which were used for making the parameters are: deg=expt<=105?4:expt<=210?5:6 or expt<=144?4:6; d=log10(c[deg])+deg*log10(m)[digits]; time=10^(d/30-4)[hours]; skew=|c0/c[deg]|^(1/deg); rlim=round(7*10^(d/60+3)); lpbr=floor(d/25+21); mfbr=floor(d/8+31); rlambda=floor(d/25+18)/10;

Efforts by ECM

The efforts by ECM to find small factors of this 208-digit composite number so far are as follows. According to the reports, unknown prime factors of this composite number are probably 30-digit or more. Please report your efforts by ECM. (Anonymous reports are not acceptable)

Level	B1	Reported runs Total / Required runs (Required runs for lower level)	Name
30	25e4	430	Makoto Kamada	Nov 3, 2008
30	25e4	430 / 430
35	1e6	0 / 825
35	1e6	/ 825
40	3e6	0 / 2336 (294)
40	3e6	/ 2336 (294)
45	11e6	0 / 4479 (677)
45	11e6	/ 4479 (677)
50	43e6	0 / 7553 (1277)
50	43e6	/ 7553 (1277)

Command line to find prime factors up to about 35-digit

echo 1854084684287800831255026300758556765515624934165962534138511682886627257448422049835732162986643665214034880887015096418780059564585634647765688001378107892556545241259313889698967281895113354080477266785803 | ecm -n -c 825 1e6

Command line to find prime factors up to about 40-digit

echo 1854084684287800831255026300758556765515624934165962534138511682886627257448422049835732162986643665214034880887015096418780059564585634647765688001378107892556545241259313889698967281895113354080477266785803 | ecm -n -c 2336 3e6

Command line to find prime factors up to about 45-digit

echo 1854084684287800831255026300758556765515624934165962534138511682886627257448422049835732162986643665214034880887015096418780059564585634647765688001378107892556545241259313889698967281895113354080477266785803 | ecm -n -c 4479 11e6

Command line to find prime factors up to about 50-digit

echo 1854084684287800831255026300758556765515624934165962534138511682886627257448422049835732162986643665214034880887015096418780059564585634647765688001378107892556545241259313889698967281895113354080477266785803 | ecm -n -c 7553 43e6

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