Sophie Germain prime
A Sophie Germain prime is a type of prime number. If a prime number is still prime after being multiplied by 2 and adding 1 to the answer, then the original prime is a Sophie Germain prime. A mathematical definition is: a prime number, denoted by p, is a Sophie Germain prime if 2p+1 is also a prime number. 2p+1 is called a safe prime if it is a prime number.