A165350 Primes p such that floor((p^2-1)/4)+p is not prime.

13, 23, 43, 53, 67, 71, 73, 79, 83, 97, 101, 103, 113, 137, 149, 157, 163, 167, 173, 179, 181, 193, 197, 211, 223, 233, 241, 257, 263, 269, 271, 277, 283, 293, 311, 313, 331, 349, 353, 373, 379, 383, 401, 409, 419, 421, 431, 433, 443, 457, 463, 467, 499

Offset: 1

Author

Vincenzo Librandi, Sep 16 2009

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A163419, A163420.

Programs

Magma

[p: p in PrimesUpTo(500)| not IsPrime(Floor((p^2-1)/4)+p)]; // Vincenzo Librandi, Sep 12 2013

Mathematica

Select[Prime[Range[2, 200]], ! PrimeQ[(#^2 - 1) / 4 + #]&] (* Vincenzo Librandi, Sep 12 2013 *)

Extensions

Edited (but not checked) by N. J. A. Sloane, Sep 25 2009