MATH STINGER #14 
by Dr. Joel C. Fowler 
Assistant Professor of Mathematics 

Here are the new puzzles. n denotes a positive integer. 
d) Explain why no number other than three of the form n^4+n^2+1 is prime. 
e) Explain why no number other than five of the form 21^n-16^n is prime. 
f) Explain why no number of the form 64^n+27^n is prime.

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