I did a search online and found a similar notion called Sophie Germain prime, which by definition is a prime $p$ such that $2p+1$ is also prime. Sophie Germain primes are conjectured to be of infinite many. I wonder if anyone has thought of the similar question replacing $2p+1$ by $2p-1$.
2026-04-11 10:39:37.1775903977
Are there infinite many primes p such that 2p-1 is also prime?
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