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Numbers k such that 7*k - 2 is prime.
2

%I #32 Sep 08 2022 08:44:48

%S 1,3,7,9,13,15,19,25,33,37,39,45,55,57,63,67,73,75,85,87,97,99,103,

%T 105,109,123,127,133,139,145,153,157,165,169,175,177,183,187,189,205,

%U 207,213,219,223,229,237,243,249,255,259,267,279,283,285,295,309,315,325,327,337,339

%N Numbers k such that 7*k - 2 is prime.

%H Vincenzo Librandi, <a href="/A024901/b024901.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A089079(n) - 3.

%t Select[Range[400], PrimeQ[7# - 2] &] (* _Vincenzo Librandi_, Sep 26 2012 *)

%o (Magma) [ n: n in [1..500] | IsPrime(7*n-2) ]; // _Vincenzo Librandi_, Nov 20 2010

%o (PARI) is(n)=isprime(7*n-2) \\ _Charles R Greathouse IV_, May 22 2017

%Y Cf. A089079.

%K nonn,easy

%O 1,2

%A _Clark Kimberling_