Show that there are no prime triplet other than $3,5,7$.
51520
Prove that the only prime triple is 3, 5, 7
68559
The sum $1+\frac{1}{3}+\frac{1}{5}+\frac{1}{7}+\cdots-(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+\cdots)$ does not exist.
44857
Why the $(n+1)$th prime number cannot exceed the smallest prime divisor of $p_1\dotsc p_n + 1$
29799
Sum of four squares not a prime
137808
$n^2 + 3n +5$ is not divisible by $121$
111935
Irreducible but not prime
136947
Simple Mersenne prime divisibility proofs
61899
Prove that the language $\{bin(p) \mid p\ \text{is prime}\}$ is not regular (prime numbers)
126494
Prove that there doesn't exist any integer $x \ge 3$ such that $x^2-1$ is prime.
85959
How do I prove that among any $5$ integers, you are able to find $3$ such that their sum is divisible by $3$?
22681
Why does Mathematica claim there is no even prime?
40968
show if $n=4k+3$ is a prime and ${a^2+b^2} \equiv 0 \pmod n$ , then $a \equiv b \equiv 0 \pmod n$
2147
Different ways to prove there are infinitely many primes?
31267
Sum of all primes under 2 million
43939
Show that $3^{2n+1}-4^{n+1}+6^n$ is never prime for natural n except 1.
77070
Prove Euler's Theorem when the integers are not relatively prime
53525
Infiniteness of non-twin primes.