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A100603
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Numbers k such that (prime(k)-1)! + prime(k)^4 is prime.
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0
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OFFSET
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1,2
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COMMENTS
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k = {1, 2, 4, 67} yields primes p(k) = {2, 3, 7, 331}. There are no more such k up to k=100. Computed in collaboration with Ray Chandler.
Terms a(5) and greater are only probable primes. - Iain Fox, Mar 05 2018
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LINKS
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FORMULA
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Numbers k such that (prime(k)-1)! + prime(k)^4 is prime, where prime(k) is the k-th prime.
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EXAMPLE
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a(3) = 4 because (prime(4)-1)! + prime(4)^4 = (7-1)! + 7^4 = 720 + 2401 = 3121 is the 3rd prime of this form.
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MATHEMATICA
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PROG
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(PARI) is(k) = my(p=prime(k)); ispseudoprime((p-1)! + p^4) \\ Iain Fox, Mar 05 2018
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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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