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Numbers n such that 2*n+19 is not a prime.
6

%I #18 Sep 08 2022 08:45:39

%S 1,3,4,7,8,10,13,15,16,18,19,22,23,25,28,29,31,33,34,36,37,38,40,43,

%T 46,48,49,50,51,52,53,55,57,58,61,62,63,64,67,68,70,71,73,75,76,78,79,

%U 82,83,84,85,88,91,92,93,94,95,97,98,99,100,101

%N Numbers n such that 2*n+19 is not a prime.

%H Vincenzo Librandi, <a href="/A153144/b153144.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[0, 500], !PrimeQ[2# + 19] &] (* _Vincenzo Librandi_, Dec 13 2012 *)

%o (Magma) [n: n in [1..120] | not IsPrime(2*n + 19)]; // _Vincenzo Librandi_, Dec 13 2012

%Y Cf. A153143, A153081, A155551.

%Y Numbers n such that 2n+k is not prime: A047845 (k=1), A153238 (k=3), A153052 (k=5), A153053 (k=7), A153723 (k=9), A153083 (k=11), A153082 (k=13), A241571 (k=15), A241572 (k=17), this sequence (k=19).

%K nonn,easy

%O 1,2

%A _Vincenzo Librandi_, Dec 19 2008