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-   -   Smallest composite without known factors "stuck" on (10^79-181)%(10^79-1)/9 (https://www.mersenneforum.org/showthread.php?t=25893)

jdcs 2020-09-01 05:31

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 [url]http://factordb.com/index.php?id=1100000000900935563[/url], but that number is actually prime.

Is it possible to fix that entry so that we can see the [B]real[/B] smallest unfactored number?

kruoli 2020-09-01 09:21

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?

retina 2020-09-01 09:28

There is a duplicate entry:
[url]http://factordb.com/index.php?id=1100000000902314000[/url]

JeppeSN 2020-09-01 11:43

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:
[url]http://factordb.com/index.php?id=1100000000900937469[/url]

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

Both these entries are entirely correct.

However, the entry you link:
[url]http://factordb.com/index.php?id=1100000000900935563[/url]
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


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