A153384 - OEIS

%I #25 Sep 08 2022 08:45:39

%S 0,1,2,5,6,7,9,11,12,15,16,20,21,22,23,26,27,29,30,31,33,34,35,36,37,

%T 38,40,41,44,45,46,49,51,53,56,57,58,59,60,61,63,64,65,66,68,70,71,72,

%U 76,77,79,80,81,82,85,86,91,92,93,94,96,97,98,100,101,102

%N Numbers n such that 24*n+1 is not prime.

%C Contains all numbers == 1 (mod 5), ==2 (mod 7), ==5 (mod 11), == 7 (mod 13), == 12 (mod 17), == 15 (mod 19), == 22 (mod 23), == 6 (mod 29) etc, so it is the union of A016861, A017005, A017449, A269044, etc. - _R. J. Mathar_, Jun 10 2020

%C Even terms of A153383, halved. - _R. J. Mathar_, Jun 10 2020

%H Vincenzo Librandi, <a href="/A153384/b153384.txt">Table of n, a(n) for n = 1..1000</a>

%e Triangle begins:

%e *;

%e *,1;

%e *,*,2;

%e *,*,*,*;

%e *,*,*,*,5;

%e *,*,*,*,*,7;

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

%e *,*,*,*,*,*,*,12;

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

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

%e *,*,*,*,*,*,*,*,*,*,22; etc.

%e where * marks the non-integer values of (2*h*k + k + h)/12 with h >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013

%t Select[Range[0, 200], !PrimeQ[24 # + 1] &] (* _Vincenzo Librandi_, Jan 14 2013 *)

%o (Magma) [n: n in [0..150] | not IsPrime(24*n + 1)]; // _Vincenzo Librandi_, Jan 14 2013

%Y Cf. A001318, A111174 (complement).

%K nonn,easy

%O 1,3

%A _Vincenzo Librandi_, Dec 25 2008

%E 0 added by _Arkadiusz Wesolowski_, Aug 03 2011