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Are there infinitely(in)finitely many primes $p$ such that $1+kp$ is a prime for some positive integer $k$ ?
Are there infinitely many primes $p$ such that $1+kp$ is a prime for some positive integer $k$ ?
Are there (in)finitely many primes $p$ such that $1+kp$ is a prime for some positive integer $k$ ?
