How do Ι show if $a^n-1$ is prime for $n >1$ then $a=2$?
59036
If $a^{n}-1$ is prime then $a=2$ and $n$ is prime?
4970
For $n \geq 2$, show that $n \nmid 2^{n}-1$
100305
Prove $2^n-1$ is divisible by $(2^m-1)^2$ iff...
102064
Prime number between $n$ and $n!+1$
140294
prove that $n >2$ and $n$ is a prime then $n$ is odd
130342
Show that for any integer a and prime p, $(a+1)^p \equiv a^p+ 1 \pmod{p}$.
66851
If $p,q$ are primes $(pq,a)=1$ and $p-1|q-1$ then prove $a^{q-1}\equiv 1\pmod{pq}$
5043
Show that $2^n>1+n\sqrt{2^{n-1}}$
131488
Show that $p^3+4$ is prime
146304
prove $(n)$ prime ideal of $\mathbb{Z}$ iff $n$ is prime or zero
143772
How can I algebraically prove that $2^n - 1$ is not always prime?
34954
If $11..11$($n$ times 1) is prime, prove that $n$ is also prime
114346
Why is $a^{-1}$ mod $p$ equal to $a^{p-2}$ mod $p$?
40968
show if $n=4k+3$ is a prime and ${a^2+b^2} \equiv 0 \pmod n$ , then $a \equiv b \equiv 0 \pmod n$
158563
If $m^4+4^n$ is prime, then $m=n=1$ or $m$ is odd and $n$ even
22742
Prove that if $p$ and $p^2+2$ are prime then $p^3+2$ is prime too
75206
If $a$, $a+2$ and $a+4$ are prime numbers then, how can one prove that there is only one solution for $a$?