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Numbers k such that 8k + 1 is prime.
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%I #35 Feb 05 2024 00:54:55

%S 2,5,9,11,12,14,17,24,29,30,32,35,39,42,44,50,51,54,56,57,65,71,72,74,

%T 75,77,80,84,95,96,101,107,110,116,117,119,122,126,129,131,137,141,

%U 144,149,150,152,156,161,162,165,170,176,179,185,186,194,200,201

%N Numbers k such that 8k + 1 is prime.

%C 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

%H T. D. Noe, <a href="/A005123/b005123.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = (A007519(n)-1)/8. - _Zak Seidov_, Sep 26 2007

%t Select[Range[0, 300], PrimeQ[8 # + 1] &] (* _Vincenzo Librandi_, Jun 25 2014 *)

%o (Magma) [n: n in [0..200] | IsPrime(8*n+1)]; // _Vincenzo Librandi_, Jun 25 2014

%o (PARI) is(n)=isprime(8*n+1) \\ _Charles R Greathouse IV_, Apr 29 2015

%Y Cf. A007519, A111174, A115249.

%K nonn

%O 1,1

%A _N. J. A. Sloane_

%E More terms from _Wesley Ivan Hurt_, Jun 25 2014