对整数a >= 2与n >= 1，a^n + 1是素数，证明
如果对某个整数
与
， 
是素数，证明n一定是2的幂。
证明：
Let 
which is not power of 2, and 
.
Obviously n is an odd number.
Then we have%5E%7Bt2%5Em%7D%20-%201%7D%7B(-a)%5E%7B2%5Em%7D%20-%201%7D%20%3D%20%5CSigma_%7Bi%20%3D%200%7D%5E%7Bt%20-%201%7D((-a)%5E%7B2m%7D)%5Ei)
.
Therefore,
hava a divisor which is 
. And this can show that is a composite number.
So n must be the power of 2.
Obviously n is an odd number.
Then we have
Therefore,
So n must be the power of 2.
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