A089593 Numbers k such that k^2 + 2k + 2 is prime.

0, 1, 3, 5, 9, 13, 15, 19, 23, 25, 35, 39, 53, 55, 65, 73, 83, 89, 93, 109, 115, 119, 123, 125, 129, 133, 145, 149, 155, 159, 169, 175, 179, 183, 203, 205, 209, 223, 229, 235, 239, 249, 255, 259, 263, 269, 279, 283, 299, 305, 313, 325, 339, 349

Offset: 1

Author

Giovanni Teofilatto, Dec 30 2003

Keywords

• nonn
• easy

References

• M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988
• Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta, UTET, CittaStudiEdizioni, Milano 1997

Links

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

Crossrefs

Cf. A002496 gives the primes, A005574, A090693.

Programs

Magma

[n: n in [0..400]|IsPrime(n^2+2*n+2)]; // Vincenzo Librandi, Dec 17 2010

Mathematica

Select[Range[0,1000],PrimeQ[#^2+2#+2]&] (* Vincenzo Librandi, May 23 2014 *)

PARI

is(n)=isprime(n^2+2*n+2) \\ Charles R Greathouse IV, Jun 12 2017

Formula

a(n) = A005574(n)-1 = A090693(n)-2.

Extensions

Corrected by Vincenzo Librandi, Dec 17 2010