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A103317
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Primes p such that p! - 1 is also prime.
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5
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OFFSET
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1,1
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COMMENTS
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The members are the primes in A002982 (n! - 1 is prime).
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, Section A2.
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LINKS
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EXAMPLE
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3 is prime and 3! - 1 = 5 is prime, so 3 is a member.
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MATHEMATICA
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PROG
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(PARI) isok(n) = ispseudoprime(n) && ispseudoprime(n!-1); \\ Jinyuan Wang, Jan 20 2020
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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a(5)=208003 (found on Jul 27 2016, by Sou Fukui), added by Jinyuan Wang, Jan 20 2020
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STATUS
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approved
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