A162237 Primes p such that p^2+3*p+1 is not prime.

11, 13, 17, 31, 41, 61, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 127, 131, 149, 151, 167, 181, 191, 193, 197, 199, 211, 223, 227, 233, 241, 251, 269, 271, 277, 281, 283, 307, 311, 317, 331, 337, 347, 367, 383, 389, 397, 401, 409, 421, 431, 433, 439, 443

Offset

1,1

Links

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

Example

p=11, p^2+3*p+1=155=5*31; p=13, p^2+3*p+1=209=11*19; p=17, p^2+3*p+1=341=11*31.

Mathematica

Select[Range[0, 500], PrimeQ[#] && !PrimeQ[#^2 + 3 # + 1] &] (* Vincenzo Librandi, Sep 11 2013

Prog

(Magma) [p: p in PrimesUpTo(500) | not IsPrime(p^2+3*p+1)]; // Vincenzo Librandi, Sep 11 2013

Crossrefs

Cf. A153590.

Sequence in context: A185104 A240570 A354524 * A325870 A090236 A240623

Adjacent sequences: A162234 A162235 A162236 * A162238 A162239 A162240

Keyword

nonn,easy

Author

Vincenzo Librandi, Jun 28 2009

Status

approved