When is $n^{2015}+n+1$ prime?
  
 
     
     
             
                 
 
 
         
         14 
         
 
         
             5 
         
 
 
 
 
             
 
             
 
     
 
 $n in mathbb{N}$.   I think this seems true only for $1$.   I tried to show that $4n-1,2n+1,2^{n+1}-1$ divides the given expression but didn't succeed. I have only thought about this through the way of modular arithmetic. Someone suggested to me to use the complex roots of this equation, but didn't specify how.  Are there any other results I can use for this problem(I may not know them)?   Please provide only hints if you do solve it. Thank you.      
 
         
             
                 number-theory elementary-number-theory polynomials prime-numbers divisibility 
             
         
 
     
         
             
  share | cite | improve this question  
             
 
                 
 
     
         edited Jan 4 at 21:58 
     
     
         
     
     
         greedoid 
         
       ...