primesieve
7.5
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Iterate backwards over primes using primesieve_iterator.Note that primesieve_next_prime() runs up to 2x faster and uses only half as much memory as primesieve_prev_prime(). Hence if it is possible to write the same algorithm using either primesieve_prev_prime() or primesieve_next_prime() then it is preferable to use primesieve_next_prime().