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A051915
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Numbers k such that 2*k! + 1 is prime.
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12
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0, 1, 2, 3, 5, 12, 18, 35, 51, 53, 78, 209, 396, 4166, 9091, 9587, 13357, 15917, 17652, 46127
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OFFSET
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1,3
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COMMENTS
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Used PrimeForm to prove primality for n = 4166 (classical N-1 test). - David Radcliffe, May 28 2007
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LINKS
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EXAMPLE
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k = 5 is here because 2*5! + 1 = 241 is prime.
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MATHEMATICA
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PROG
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(Magma) [n: n in [0..1000] | IsPrime(2*Factorial(n) +1)]; // Vincenzo Librandi, Feb 21 2015
(PARI) is(k) = ispseudoprime(2*k!+1); \\ Jinyuan Wang, Feb 05 2020
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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