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Old 2019-02-16, 18:10   #1
neskis
 
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Feb 2019

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Default Primality based on digital root

Hi!

Has anyone besides me noticed this?

Primes are the sum of two CONSECUTIVE integers ONLY as follows:

Prime DR1 = integer DR0 + integer DR1
Prime DR2 = integer DR5 + integer DR6
Prime DR4 = integer DR6 + integer DR7
Prime DR5 = integer DR2 + integer DR3
Prime DR7 = integer DR3 + integer DR4
Prime DR8 = integer DR8 + integer DR0
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Old 2019-02-16, 20:01   #2
Batalov
 
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Mar 2008
Phi(4,2^7658614+1)/2

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Default

Yeah. And it has nothing to do with "primes". Primes in your message is a red herring.

This is called modular arithmetic. Look it up.


DR is nothing else than mod(9).
What you are doing is: using mod(9) you are trying to solve:
x + (x+1) = a (mod 9).
But the solution is obvious:
x = (a-1)/2 (mod 9)


Example:
you are saying: "DR4 = integer DR6 + integer DR7".
Or in other words: "4 = 6+7 (mod 9)".
That's obvious, because 6 = (4-1)/2 (mod 9).

(look up how to divide by 2 in a modular system)
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