Sophie Germain prime

This article defines a property that can be evaluated for a prime number. In other words, every prime number either satisfies this property or does not satisfy this property.
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Definition

A Sophie Germain prime is a prime number $p$ such that $2p+1$ is also prime. The corresponding prime $2p+1$ is termed a safe prime.

Testing

The ID of the sequence in the Online Encyclopedia of Integer Sequences is A005384