A152843 - OEIS

%I #10 Sep 08 2022 08:45:39

%S 0,1,4,10,13,19,25,40,43,55,64,85,88,94,115,118,124,139,145,178,208,

%T 214,220,244,253,295,319,325,328,340,358,370,379,403,454,475,505,508,

%U 514,523,550,610,613,643,703,718,724,739,748,754,778,790,799,865,904,943

%N Numbers n such that both 2n+3 and 4n+7 are prime.

%C Or, numbers n such that 2n+3 is a Sophie Germain prime. [_Klaus Brockhaus_, Dec 22 2008]

%H Vincenzo Librandi, <a href="/A152843/b152843.txt">Table of n, a(n) for n = 1..1000</a>

%e For n = 10, 2*n+3 = 23 is prime and 4*n+7 = 47 is prime. 23 = A005384(5).

%t Join[{0}, Select[Range[1000], PrimeQ[2*#+3] && PrimeQ[4*#+7] &]] (* _Vincenzo Librandi_, Aug 30 2012 *)

%t Select[Range[0,1000],AllTrue[{2#+3,4#+7},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Aug 07 2015 *)

%o (Magma) [ n: n in [0..1000] | IsPrime(2*n+3) and IsPrime(4*n+7) ];

%Y Cf. A067076 (2n+3 is prime), A089986 (4n+7 is prime), A005384 (Sophie Germain primes).

%K nonn,easy

%O 1,3

%A _Vincenzo Librandi_, Dec 14 2008

%E Edited and extended by _Klaus Brockhaus_, Dec 22 2008