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%I #13 Sep 08 2022 08:45:41
%S 1,3,4,5,7,9,10,11,12,13,14,15,16,17,19,20,21,22,23,25,26,27,28,29,30,
%T 31,33,34,35,36,37,39,40,41,42,43,45,46,47,48,49,50,51,52,53,54,55,57,
%U 58,59,60,61,63,64,65,67,68,69,70,71,73,75,76,77,79,80,81
%N Numbers n such that 13*n + 5 is not prime.
%H Vincenzo Librandi, <a href="/A155935/b155935.txt">Table of n, a(n) for n = 1..1000</a>
%e Distribution of the even terms in the following triangular array::
%e *;
%e *,*;
%e *,*,*;
%e *,*,*,*;
%e *,*,*,*,*;
%e *,*,*,*,*,*;
%e *,*,*,10,*,*,*;
%e *,*,*,*,14,*,*,*;
%e 4,*,*,*,*,*,*,*,*;
%e *,*,*,*,*,*,*,*,*,*;
%e *,*,12,*,*,*,*,*,*,*,*;
%e *,*,*,*,*,*,*,*,*,40,*,*; etc.
%e where * marks the non-integer values of (4*h*k + 2*k + 2*h - 4)/13 with h >= k >= 1. - _Vincenzo Librandi_, Jan 15 2013
%t Select[Range[0, 100], !PrimeQ[13 # + 5] &] (* _Vincenzo Librandi_, Oct 15 2012 *)
%o (Magma) [n: n in [0..90] | not IsPrime(13*n + 5)];
%Y Cf. A102732, A154610.
%K nonn,easy
%O 1,2
%A _Vincenzo Librandi_, Jan 31 2009
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