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A100599
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Numbers k such that (prime(k)-1)! + prime(k)^7 is prime.
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2
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OFFSET
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1,1
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COMMENTS
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k = {7, 14, 16, 59} yields primes p(k) = {17, 43, 53, 277}. There are no more such k up to k=100. Computed in collaboration with Ray Chandler.
a(5) > 600. - Jinyuan Wang, Apr 10 2020
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LINKS
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Table of n, a(n) for n=1..4.
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FORMULA
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Numbers k such that (prime(k)-1)! + prime(k)^7 is prime, where prime(k) is the k-th prime.
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EXAMPLE
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a(7) = 7 because (prime(7)-1)! + prime(7)^7 = (17-1)! + 17^7 = 20923200226673 is the smallest prime of that form.
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MATHEMATICA
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lst={}; Do[p=Prime[n]; If[PrimeQ[(p-1)!+p^7], AppendTo[lst, n]], {n, 10^2}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 08 2008 *)
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PROG
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(PARI) is(k) = ispseudoprime((prime(k)-1)! + prime(k)^7); \\ Jinyuan Wang, Apr 10 2020
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CROSSREFS
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Cf. A100598, A100600, A100858.
Sequence in context: A269173 A167197 A336797 * A198390 A118905 A254064
Adjacent sequences: A100596 A100597 A100598 * A100600 A100601 A100602
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KEYWORD
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nonn,hard,more
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AUTHOR
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Jonathan Vos Post, Nov 30 2004
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STATUS
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approved
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