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Numbers n such that 12*n+5 is not prime.
1

%I #13 Sep 08 2022 08:45:48

%S 5,6,10,13,15,17,18,20,25,27,28,30,31,34,35,36,39,40,41,44,45,48,50,

%T 52,55,57,59,60,61,62,65,69,70,72,74,75,76,80,82,83,85,86,89,90,93,94,

%U 95,96,97,100,103,104,105,109,110,111,112,115,116,118,120,121,122,125,126

%N Numbers n such that 12*n+5 is not prime.

%H Vincenzo Librandi, <a href="/A166563/b166563.txt">Table of n, a(n) for n = 1..1000</a>

%e Distribution of the terms in the following triangular array:

%e *;

%e *,*;

%e *,*,*;

%e *,*,*,*;

%e *,*,6,*,*;

%e *,5,*,*,*,*;

%e *,*,*,*,*,*,*;

%e *,*,*,*,*,18,*,*;

%e *,*,*,*,17,*,*,*,*;

%e *,*,*,*,*,*,*,*,*,*;

%e *,*,13,*,*,*,*,*,36,*,*;

%e *,10,*,*,*,*,*,35,*,*,*,*; etc.

%e where * marks the non-integer values of (2*h*k + k + h - 2)/6 with h >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013

%t Select[Range[0, 200], !PrimeQ[12 # + 5] &] (* _Vincenzo Librandi_, Jan 14 2013 *)

%o (Magma) [n: n in [0..150] | not IsPrime(12*n+5)]; // _Vincenzo Librandi_, Jan 14 2013

%Y Cf. A167055.

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_, Oct 29 2009