Twin prime
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If n is a natural number, and 6n-1 is prime, and so is 6n+1, then 6n-1 and 6n+1 are said to be a set of twin primes.
If n is a natural number, and 6n-1 is prime, and so is 6n+1, then 6n-1 and 6n+1 are said to be a set of twin primes.