Problem 896. Sophie Germain prime
In number theory, a prime number p is a Sophie Germain prime if 2p + 1 is also prime. For example, 23 is a Sophie Germain prime because it is a prime and 2 × 23 + 1 = 47, and 47 is also a prime number. These numbers are named after French mathematician Marie-Sophie Germain.
See Sophie Germain prime article on Wikipedia.
In this Problem , the input is a number and you must return true or false if this number is a Sophie Germain prime.
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