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A082182
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Numbers n such that (5^n-2^n)/3 is prime.
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20
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2, 5, 7, 13, 19, 37, 59, 67, 79, 307, 331, 599, 1301, 12263, 12589, 18443, 20149, 27983
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OFFSET
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1,1
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COMMENTS
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No other terms less than 100000. - Robert Price, Apr 06 2012
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LINKS
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Table of n, a(n) for n=1..18.
User group for the PrimeForm program.
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EXAMPLE
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Example: a(1)=2 because (5^2-2^2)/3=(25-4)/3=7 is a prime.
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MATHEMATICA
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a={}; Do[p=(5^n-2^n)/3; If[PrimeQ[p], AppendTo[a, n]], {n, 20^2}]; Print[a]; - Vladimir Joseph Stephan Orlovsky, Apr 29 2008
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PROG
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(PARI) forprime(p=2, 1e4, if(ispseudoprime((5^p-2^p)/3), print1(p", "))) \\ Charles R Greathouse IV, Jul 16, 2011
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CROSSREFS
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Sequence in context: A094743 A175075 A056985 * A032719 A045355 A165319
Adjacent sequences: A082179 A082180 A082181 * A082183 A082184 A082185
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KEYWORD
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more,nonn,changed
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AUTHOR
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Hugo Pfoertner, May 22 2003, Jun 23 2003
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EXTENSIONS
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20149 from Herman Jamke (hermanjamke(AT)fastmail.fm), May 03 2007
27983 from David Radcliffe, May 28 2007
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STATUS
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approved
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