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A005123 Numbers n such that 8n + 1 is prime. 22
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = (A007519(n)-1)/8. - Zak Seidov, Sep 26 2007

MATHEMATICA

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 *)

PROG

(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

CROSSREFS

Cf. A007519, A111174, A115249.

Sequence in context: A110781 A170838 A115248 * A283481 A284875 A154732

Adjacent sequences:  A005120 A005121 A005122 * A005124 A005125 A005126

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Wesley Ivan Hurt, Jun 25 2014

STATUS

approved

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Last modified April 20 22:22 EDT 2019. Contains 322310 sequences. (Running on oeis4.)