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A138595
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Numbers n such that 2^(2*n-21)-21 is prime.
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0
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11, 12, 13, 14, 15, 16, 17, 21, 22, 31, 55, 205, 217, 255
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..14.
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EXAMPLE
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2^(2*13-21)-21=11, 2^(2*14-21)-21=107, 2^(2*15-21)-21=491, 2^(2*16-21)-21=2027, ...
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MATHEMATICA
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q=21; For[i=q, i<=q, a={}; Do[x=2^(2*n-i)-i; If[PrimeQ[x], AppendTo[a, n]], {n, 10^2}]; Print["2^(2*n-", i, ")-", i, " ", a]; i=i+2]
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PROG
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(PARI) is(n)=isprime(2^(2*n-21)-21) \\ Charles R Greathouse IV, Jun 13 2017
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CROSSREFS
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Sequence in context: A297269 A296710 A297143 * A192271 A214423 A185300
Adjacent sequences: A138592 A138593 A138594 * A138596 A138597 A138598
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KEYWORD
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nonn,easy
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AUTHOR
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Vladimir Joseph Stephan Orlovsky, May 13 2008
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STATUS
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approved
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