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Search: id:A087885
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| A087885 |
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Numbers n such that 5^n +2 is a prime. |
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+0
10
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| 1, 3, 17, 143, 261, 551, 2285, 18731, 18995, 19751, 62067
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Terms <= 551 correspond to certified primes. Next term after 2285 is greater than 10000.
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LINKS
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Henri & Renaud Lifchitz, PRP Records.
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EXAMPLE
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a(2)=3 is a member because 5^3 +2 = 127 is a prime.
5^17 + 2 = 762939453127 is prime, hence 17 is a term.
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MATHEMATICA
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Do[If[PrimeQ[5^n + 2], Print[n]], {n, 1, 10000}] (Propper)
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CROSSREFS
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Cf. A051783, 3^n +2 is a prime.
Sequence in context: A136727 A120022 A001865 this_sequence A051442 A162650 A015735
Adjacent sequences: A087882 A087883 A087884 this_sequence A087886 A087887 A087888
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KEYWORD
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hard,nonn
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AUTHOR
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Donald S. McDonald (don.mcdonald(AT)paradise.net.nz), Oct 13 2003
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EXTENSIONS
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Two more terms from Ryan Propper (rpropper(AT)stanford.edu), Jun 17 2005
{18731, 18995, 19751, 62067} found by Mike Oakes in 2003. - Alexander Adamchuk (alex(AT)kolmogorov.com), Mar 02 2008
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