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-   -   Faster than LL? (https://www.mersenneforum.org/showthread.php?t=2540)

clowns789 2004-05-27 21:23

Faster than LL?
 
Please tell me if this is pretty obvious.

I noticed that any composite number over 3 could have two primes added up to equal it.

For example:

You want to check if 11 is prime. You go down to the next highest prime, 7. 7+2=9, 7+3=10. Any higher would make what it equals higher. You go down to 5 and find you can't add anything to make it up to 11. Therefore, it is prime.

Tell me how you like it. It seemed pretty simple so I don't think it will actually beat LL.

Uncwilly 2004-05-27 21:36

What is the next highest prime to M41?

You have to have knowledge of all primes lower than the number in question, this makes it impractical for titanic numbers, even just hugh numbers.

cyrix 2004-05-27 21:45

[QUOTE=clowns789]Please tell me if this is pretty obvious.

I noticed that any composite number over 3 could have two primes added up to equal it.

[/QUOTE]

Which two primes add to 35? :surprised

Cyrix

Mike 2004-05-27 23:39

[QUOTE=cyrix]Which two primes add to 35? :surprised

Cyrix[/QUOTE]

I keep getting 34 :rolleyes: But it works if 3 primes are allowed to be added.


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