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Old 2005-11-10, 16:04   #12
axn
 
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Quote:
Originally Posted by Citrix
See http://mathworld.wolfram.com/WilsonsTheorem.html
the formula comes from wilson's theorem
Aah! I see. Thank you!
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Old 2005-11-10, 18:12   #13
Citrix
 
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p=2,23,53,853

Are the only case for which sum of first p primes =0 (mod p). (under 5 Million)
I have searched the first 5 million primes and am continuing. No solution yet.

Citrix
edit: Are there any more of this type. The probability is 1/p. (which is not so bad)

Last fiddled with by Citrix on 2005-11-10 at 18:27
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Old 2005-11-10, 18:39   #14
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checked the first 12.5 Million primes ie primes under 230 Million.

Citrix
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Old 2005-11-10, 20:10   #15
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The above problem can be solved if some one can prove this or disprove the following. It might already have been conjectured by some one or proved by some one.

For every even number n >4 there exists a prime t < n/2 such that n+t is also prime!

(checked to 1M)

If this is the case then for us, consider a n=2*p
Then t=n+t (mod p)
And there are no more solutions to the problem, other than 2.

Last fiddled with by Citrix on 2005-11-10 at 20:24
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Old 2005-11-10, 20:25   #16
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n>4 should be n>7
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Old 2005-11-10, 21:00   #17
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Quote:
Originally Posted by Citrix
p=2,23,53,853

Are the only case for which sum of first p primes =0 (mod p). (under 5 Million)
I have searched the first 5 million primes and am continuing. No solution yet.
It makes sense to submit this sequence to OEIS.
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Old 2005-11-10, 21:36   #18
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Submitted the sequence.

For product


((p(2)#/2)+1)%2 is Zero (0)
((p(241)#/241)+1)%241 is Zero (0)
((p(271)#/271)+1)%271 is Zero (0)
((p(8627)#/8627)+1)%8627 is Zero (0)

No more till 200,000.

Citrix
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