A153082 - OEIS

%I #24 Sep 08 2022 08:45:39

%S 1,4,6,7,10,11,13,16,18,19,21,22,25,26,28,31,32,34,36,37,39,40,41,43,

%T 46,49,51,52,53,54,55,56,58,60,61,64,65,66,67,70,71,73,74,76,78,79,81,

%U 82,85,86,87,88,91,94,95,96,97,98,100,101,102,103,104,106,109,111

%N Numbers k such that 2*k + 13 is not prime.

%C One less than the associated entry in A153083. - _R. J. Mathar_, Jan 05 2011

%H Vincenzo Librandi, <a href="/A153082/b153082.txt">Table of n, a(n) for n = 1..1000</a>

%e Distribution in the following triangular array:

%e *;

%e 1, 6;

%e 4, 11,18;

%e 7, 16,25,34;

%e 10,21,32,43,54;

%e 13,26,39,52,65,78;

%e 16,31,46,61,76,91,106;

%e 19,36,53,70,87,104,121,138;

%e 22,41,60,79,98,117,136,155,174;

%e 25,46,67,88,109,130,151,172,193,214;

%e 28,51,74,97,120,143,166,189,212,235,258;

%e 31,56,81,106,131,156,181,206,231,256,281,306;

%e 34,61,88,115,142,169,196,223,250,277,304,331,358; etc.

%e where * marks the negative values of (2*h*k + k + h - 6) with h >= k >= 1. -

%e _Vincenzo Librandi_, Jan 15 2013

%t Select[Range[0,100],!PrimeQ[2#+13]&]  (* _Harvey P. Dale_, Mar 17 2011 *)

%o (Magma) [n: n in [1..120] | not IsPrime(2*n + 13)]; // _Vincenzo Librandi_, Nov 21 2012

%Y Cf. A153081, A153083, A155550, A153053.

%K nonn,easy

%O 1,2

%A _Vincenzo Librandi_, Dec 18 2008