A153403 - OEIS

%I #15 Sep 08 2022 08:45:39

%S 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 48,49,51,53,54,55,57,58,60,62,63,66,69,70,71,72,75,76,78,79,80,81,83,

%U 84,87,89,90,91,92,93,94,96,97,99,100

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

%H Vincenzo Librandi, <a href="/A153403/b153403.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 *,*,6,*;

%e 3,*,*,*,*;

%e *,*,*,*,14,*;

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

%e *,*,*,15,*,*,*,*;

%e *,*,13,*,*,*,*,32,*;

%e 6,*,*,*,*,27,*,*,*,*;

%e *,*,*,*,25,*,*,*,*,48,*; etc.

%e where * marks the non-integer values of (2*h*k + k + h - 1)/5 with n >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013

%t lst={};Do[p=10*n+3;If[ !PrimeQ[p],AppendTo[lst,n]],{n,0,6!}];lst (* _Vladimir Joseph Stephan Orlovsky_, May 12 2010 *)

%o (Magma) [n: n in [0..150] | not IsPrime(10*n + 3)]; // _Vincenzo Librandi_, Jan 14 2013

%Y Cf. A102338.

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_, Dec 25 2008