A153464 - OEIS

%I #26 Oct 05 2024 09:39:45

%S 0,3,4,6,9,10,12,14,15,17,18,19,21,24,27,28,29,30,31,33,34,36,38,39,

%T 40,42,44,45,48,49,50,51,52,53,54,57,59,60,61,63,64,66,69,70,72,73,74,

%U 75,78,79,80,81,83,84,87,88,89,90,92,93,94,96,99,101,102,104,105

%N Numbers k such that 4*k+9 is not prime.

%H Vincenzo Librandi, <a href="/A153464/b153464.txt">Table of n, a(n) for n = 1..1000</a>

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

%e   0;

%e   *,4;

%e   3,*,10;

%e   *,9,*,18;

%e   6,*,17,*,28;

%e   *,14,*,27,*,40;

%e   9,*,24,*,39,*,54;

%e   *,19,*,36,*,53,*,70;

%e   12,*,31,*,50,*,69,*,88;

%e   *,24,*,45,*,66,*,87,*,108;

%e   15,*,38,*,61,*,84,*,107,*,130; etc.

%e where * marks the non-integer values of (2*h*k + k + h - 4)/2 with h >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013

%t Select[Range[0, 200], !PrimeQ[4 # + 9] &] (* _Vincenzo Librandi_, Jan 14 2013 *)

%o (Magma) [n: n in [0..150] | not IsPrime(4*n+9)]; // _Vincenzo Librandi_, Jan 14 2013

%Y Cf. A111199.

%K nonn,easy

%O 1,2

%A _Vincenzo Librandi_, Dec 27 2008

%E 79 added by _R. J. Mathar_, Sep 23 2009

%E 0 added by _Arkadiusz Wesolowski_, Aug 03 2011