mersenneforum.org  

Go Back   mersenneforum.org > Factoring Projects > FactorDB

Reply
 
Thread Tools
Old 2020-09-01, 05:31   #1
jdcs
 
Sep 2019

23 Posts
Default Smallest composite without known factors "stuck" on (10^79-181)%(10^79-1)/9

The "Smallest composite without known factors" on the status page often points to http://factordb.com/index.php?id=1100000000900935563, but that number is actually prime.

Is it possible to fix that entry so that we can see the real smallest unfactored number?
jdcs is offline   Reply With Quote
Old 2020-09-01, 09:21   #2
kruoli
 
kruoli's Avatar
 
"Oliver"
Sep 2017
Porta Westfalica, DE

331 Posts
Default

It thinks that 1551548344191988309623860115843108935500421 is a factor of that number for some reason. Maybe it thinks it is composite because it evaluates the expression to 1111111111111111111111111111111111111111111111111111111111111111111111111110931 and not 1111111111111111111111111111111111111111111111111111111111111111111111111111091?
kruoli is online now   Reply With Quote
Old 2020-09-01, 09:28   #3
retina
Undefined
 
retina's Avatar
 
"The unspeakable one"
Jun 2006
My evil lair

2·32·17·19 Posts
Default

There is a duplicate entry:
http://factordb.com/index.php?id=1100000000902314000
retina is offline   Reply With Quote
Old 2020-09-01, 11:43   #4
JeppeSN
 
JeppeSN's Avatar
 
"Jeppe"
Jan 2016
Denmark

101000002 Posts
Default

There must be or have been some inconsistence on how the precedence is when the parentheses are not explicit.

If you type (10^79-181)%((10^79-1)/9) you come to the fully factored 79-digit composite number:
http://factordb.com/index.php?id=1100000000900937469

If you type ((10^79-181)%(10^79-1))/9 you come to the 79-digit prime:
http://factordb.com/index.php?id=1100000000902314000

Both these entries are entirely correct.

However, the entry you link:
http://factordb.com/index.php?id=1100000000900935563
seems to be a mix-up of the two interpretations. It has evaluated to "C" (composite). But when you click Show digits, you see the expansion for the 79-digit prime.

I speculate that one piece of code in factordb sees the expression in one way, and another place sees it in the other way, and we have this mix-up. The schizophrenic entry needs to be removed, and (if not fixed already) the operator precedence convention must be consequent.

/JeppeSN
JeppeSN is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is "mung" or "munged" a negative word in a moral sense? Uncwilly Lounge 15 2020-04-14 18:35
How much smaller can "primitive" factors be? jshort Other Mathematical Topics 5 2019-12-21 16:19
"factors.txt.u1conflict..." files Flatlander Linux 3 2011-02-21 02:32
"On factors of Mersenne numbers" - Seiji Tomita cheesehead Math 6 2009-12-15 17:45
Would Minimizing "iterations between results file" may reveal "is not prime" earlier? nitai1999 Software 7 2004-08-26 18:12

All times are UTC. The time now is 17:01.

Mon Oct 26 17:01:15 UTC 2020 up 46 days, 14:12, 0 users, load averages: 1.89, 1.84, 1.76

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.