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 2004-05-27, 21:23 #1 clowns789     Jun 2003 The Computer 17E16 Posts 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.
 2004-05-27, 21:36 #2 Uncwilly 6809 > 6502     """"""""""""""""""" Aug 2003 101×103 Posts 871910 Posts 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.
2004-05-27, 21:45   #3
cyrix

Jul 2003
Thuringia; Germany

5810 Posts

Quote:
 Originally Posted by 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.
Which two primes add to 35? :surprised

Cyrix

Last fiddled with by cyrix on 2004-05-27 at 21:46

2004-05-27, 23:39   #4
Mike

May 2004
Vancouver, Canada

22×52 Posts

Quote:
 Originally Posted by cyrix Which two primes add to 35? :surprised Cyrix
I keep getting 34 But it works if 3 primes are allowed to be added.

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