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A153403 Numbers n such that 10*n+3 is not prime.

%I A153403 #17 Jan 19 2025 16:39:15
%S A153403 3,6,9,12,13,14,15,18,20,21,24,25,27,30,32,33,34,36,39,40,41,42,45,47,
%T A153403 48,49,51,53,54,55,57,58,60,62,63,66,69,70,71,72,75,76,78,79,80,81,83,
%U A153403 84,87,89,90,91,92,93,94,96,97,99,100
%N A153403 Numbers n such that 10*n+3 is not prime.
%H A153403 Vincenzo Librandi, <a href="/A153403/b153403.txt">Table of n, a(n) for n = 1..1000</a>
%e A153403 Distribution of the terms in the following triangular array:
%e A153403 *;
%e A153403 *,*;
%e A153403 *,*,*;
%e A153403 *,*,6,*;
%e A153403 3,*,*,*,*;
%e A153403 *,*,*,*,14,*;
%e A153403 *,*,*,*,*,*,*;
%e A153403 *,*,*,15,*,*,*,*;
%e A153403 *,*,13,*,*,*,*,32,*;
%e A153403 6,*,*,*,*,27,*,*,*,*;
%e A153403 *,*,*,*,25,*,*,*,*,48,*; etc.
%e A153403 where * marks the non-integer values of (2*h*k + k + h - 1)/5 with n >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013
%t A153403 lst={};Do[p=10*n+3;If[ !PrimeQ[p],AppendTo[lst,n]],{n,0,6!}];lst (* _Vladimir Joseph Stephan Orlovsky_, May 12 2010 *)
%t A153403 Select[Range[100],CompositeQ[10#+3]&] (* _Harvey P. Dale_, Jan 19 2025 *)
%o A153403 (Magma) [n: n in [0..150] | not IsPrime(10*n + 3)]; // _Vincenzo Librandi_, Jan 14 2013
%Y A153403 Cf. A102338.
%K A153403 nonn,easy
%O A153403 1,1
%A A153403 _Vincenzo Librandi_, Dec 25 2008