%I #21 Sep 08 2022 08:44:48
%S 1,3,5,9,11,15,23,29,33,35,39,41,45,51,53,59,69,75,81,83,89,93,95,111,
%T 113,119,123,135,141,143,149,159,161,165,171,179,183,185,189,195,209,
%U 213,221,225,231,233,239,243,251,261,269,273,279,299,305,321,335,341
%N Numbers k such that 7*k - 4 is prime.
%H Vincenzo Librandi, <a href="/A024903/b024903.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A033868(n-1)-1 = A089033(n-1)+1 = A090614(n-1)*2+1.
%t Select[Range[350], PrimeQ[7 # - 4] &] (* _Vincenzo Librandi_, Sep 26 2012 *)
%o (Magma) [n: n in [1..400] | IsPrime(7*n-4)]; // _Vincenzo Librandi_, Nov 20 2010
%o (PARI) is(n)=isprime(7*n-4) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y Cf. A045437 (associated primes), A090613 (gives prime index).
%Y Cf. A033868, A089033, A090614.
%K nonn,easy
%O 1,2
%A _Clark Kimberling_