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%I #17 Sep 08 2022 08:45:47
%S 13,23,43,53,67,71,73,79,83,97,101,103,113,137,149,157,163,167,173,
%T 179,181,193,197,211,223,233,241,257,263,269,271,277,283,293,311,313,
%U 331,349,353,373,379,383,401,409,419,421,431,433,443,457,463,467,499
%N Primes p such that floor((p^2-1)/4)+p is not prime.
%H Vincenzo Librandi, <a href="/A165350/b165350.txt">Table of n, a(n) for n = 1..1000</a>
%t Select[Prime[Range[2, 200]], ! PrimeQ[(#^2 - 1) / 4 + #]&] (* _Vincenzo Librandi_, Sep 12 2013 *)
%o (Magma) [p: p in PrimesUpTo(500)| not IsPrime(Floor((p^2-1)/4)+p)]; // _Vincenzo Librandi_, Sep 12 2013
%Y Cf. A163419, A163420.
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Sep 16 2009
%E Edited (but not checked) by _N. J. A. Sloane_, Sep 25 2009
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