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A005123
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Numbers n such that 8n + 1 is prime.
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22
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2, 5, 9, 11, 12, 14, 17, 24, 29, 30, 32, 35, 39, 42, 44, 50, 51, 54, 56, 57, 65, 71, 72, 74, 75, 77, 80, 84, 95, 96, 101, 107, 110, 116, 117, 119, 122, 126, 129, 131, 137, 141, 144, 149, 150, 152, 156, 161, 162, 165, 170, 176, 179, 185, 186, 194, 200, 201
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OFFSET
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1,1
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COMMENTS
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Solutions of the equation (8*n+1)'=1, where n' is the arithmetic derivative of n. - Paolo P. Lava, Jan 03 2013
4*a(n) is the degree of the minimal polynomial of 2*cos(Pi/A007519(n)), called C(A007519(n), x) in A187360. - Wolfdieter Lang, Oct 24 2013
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..1000
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FORMULA
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a(n) = (A007519(n)-1)/8. - Zak Seidov, Sep 26 2007
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MATHEMATICA
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a={}; Do[x=8*n+1; If[PrimeQ[x], AppendTo[a, n]], {n, 10^2}]; a (* Vladimir Joseph Stephan Orlovsky, Apr 29 2008 *)
Select[Range[0, 300], PrimeQ[8 # + 1] &] (* Vincenzo Librandi, Jun 25 2014 *)
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PROG
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(MAGMA) [n: n in [0..200] | IsPrime(8*n+1)]; // Vincenzo Librandi, Jun 25 2014
(PARI) is(n)=isprime(8*n+1) \\ Charles R Greathouse IV, Apr 29 2015
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CROSSREFS
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Cf. A007519, A111174, A115249.
Sequence in context: A110781 A170838 A115248 * A283481 A284875 A154732
Adjacent sequences: A005120 A005121 A005122 * A005124 A005125 A005126
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane
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EXTENSIONS
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More terms from Wesley Ivan Hurt, Jun 25 2014
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STATUS
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approved
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