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A162237 Primes p such that p^2+3*p+1 is not prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A266675 A185104 A240570 * A325870 A090236 A240623

Adjacent sequences:  A162234 A162235 A162236 * A162238 A162239 A162240

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Jun 28 2009

STATUS

approved

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Last modified June 24 21:51 EDT 2022. Contains 354830 sequences. (Running on oeis4.)