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An exponent and prime problem (Posted on 2007-01-06) Difficulty: 2 of 5
Given that n is a positive prime number. Determine analytically all possible n such that 2n + n2 is a prime number.

See The Solution Submitted by K Sengupta    
Rating: 4.0000 (2 votes)

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Some Thoughts needs a second attempt | Comment 1 of 6

All odd numbers n. Because for a given odd number n, 2^n will be a number which either ends in 8 or 2. and then n^2 ends in 9 or 7 respectively. So the number ends with 7 no matter what is the value of odd n.

I will attempt this again tommorrow, when I wake up.


  Posted by elementofsurprize on 2007-01-06 14:42:54
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