A153235 - OEIS

%I #18 Sep 08 2022 08:45:39

%S 1,4,6,7,10,11,13,14,16,17,19,21,22,25,26,28,30,31,34,35,36,37,39,40,

%T 41,42,43,46,48,49,50,51,52,55,56,58,61,63,64,65,66,67,68,69,70,71,72,

%U 73,76,77,79,81,82,83,84,85,86,87,88,91,94,95,96,97,98,99,100,101

%N Numbers n such that 8*n+7 is not prime.

%H Vincenzo Librandi, <a href="/A153235/b153235.txt">Table of n, a(n) for n = 1..1000</a>

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

%e *;

%e 1,*;

%e *,*,*;

%e *,*,7,*;

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

%e 4,*,*,*,17,*;

%e *,*,*,16,*,*,*;

%e *,*,14,*,*,*,31,*;

%e *,11,*,*,*,30,*,*,*;

%e 7,*,*,*,28,*,*,*,49,*:

%e *,*,*,25,*,*,*,48,*,*,*;

%e *,*,21,*,*,*,46,*,*,*,71,*; etc.

%e where * marks the non-integer values of (2*h*k + k + h - 3)/4 with h >= k >= 1. - _Vincenzo Librandi_, Jan 15 2013

%t Select[Range[0, 200], !PrimeQ[8 # + 7] &] (* _Vincenzo Librandi_, Jan 12 2013 *)

%o (Magma) [n: n in [0..110] | not IsPrime(8*n+7)]; // _Vincenzo Librandi_, Jan 12 2013

%Y Cf. A139487.

%K nonn,easy

%O 1,2

%A _Vincenzo Librandi_, Dec 21 2008