A165637 - OEIS

%I #16 Sep 08 2022 08:45:48

%S 2,17,43,53,59,61,71,83,89,107,113,127,131,137,139,149,163,167,173,

%T 179,181,191,193,199,223,229,241,251,269,271,277,281,283,311,313,317,

%U 347,373,379,383,401,419,421,431,433,439,457,461,467,479,499,503,523,541,557,563

%N Primes p such that (p^2-3)/2 is not a prime number.

%H Vincenzo Librandi, <a href="/A165637/b165637.txt">Table of n, a(n) for n = 1..1000</a>

%F A000040 \ A110589. - _R. J. Mathar_, Sep 26 2009

%e For p=17=a(2), (17^2-3)/2=143 is not a prime. For p=43=a(3), (43^2-3)/2=923 is not a prime.

%t Select[Prime[Range[200]], !PrimeQ[(#^2 - 3) / 2]&] (* _Harvey P. Dale_, Dec 09 2011 *)

%o (Magma) [p: p in PrimesUpTo(600)| not IsPrime((p^2-3) div 2)]; // _Vincenzo Librandi_, Sep 12 2013

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_, Sep 23 2009

%E Extended by _R. J. Mathar_, Sep 26 2009