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A344991
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Numbers k such that (2*k+1)*k!-1 is prime.
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1
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1, 3, 5, 15, 20, 44, 45, 73, 80, 93, 295, 5395
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OFFSET
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1,2
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COMMENTS
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a(13) > 10^4.
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LINKS
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MAPLE
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select(k -> isprime((2*k+1)*k!-1), [$1 .. 300])[];
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MATHEMATICA
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Do[If[PrimeQ[(2*k + 1)*Factorial[k] - 1], Print[k]], {k, 1, 3000}]
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PROG
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(PARI) for(k=1, 3000, if(isprime((2*k+1)*k!-1), print1(k", ")))
(SageMath)
for k in range(1, 3000):
if is_prime((2*k+1)*factorial(k) - 1):
print(k)
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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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STATUS
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approved
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