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2^a*3^b one away from a prime   Message List  
Reply Message #21119 of 21307 |
Given any prime expressed as a+b, is there always some a,b such that 2^a*3^b is
one away from a prime?

I doubt it but have yet to find a counterexample.

Below are primes < 3187 which produced five or fewer solutions. [prime, number
of times that 2^a*3^b is one away from a prime]

[2, 2] [3, 3] [5, 5] [11, 5] [317, 5] [347, 3] [677, 4] [739, 4] [809,
5] [857, 5] [1033, 5] [1229, 5] [1291, 5] [1319, 5] [1451, 2] [1471, 5]
[1663, 3] [1721, 5] [2069, 4] [2477, 5] [2659, 4] [2677, 3]

Mark




Thu Nov 19, 2009 3:59 pm

marku606
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Message #21119 of 21307 |
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Given any prime expressed as a+b, is there always some a,b such that 2^a*3^b is one away from a prime? I doubt it but have yet to find a counterexample. Below...
marku606
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Nov 19, 2009
3:59 pm

... I expect infinitely many counter examples but there are none below 7500. I only computed one prime for each prime sum a+b. -- Jens Kruse Andersen...
Jens Kruse Andersen
jkand71
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Nov 19, 2009
10:39 pm

... I think you're right Jens, infinitely many. By observation, the average number of solutions for a given prime seems to be roughly constant, around 10. For...
marku606
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Nov 20, 2009
4:33 am
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