A089747 Numbers n such that n^2 - 2n + 5 is prime.

0, 2, 4, 6, 8, 14, 16, 18, 28, 34, 36, 38, 46, 48, 58, 66, 68, 74, 86, 88, 96, 98, 104, 116, 118, 126, 136, 138, 148, 156, 164, 168, 178, 184, 194, 204, 208, 216, 218, 234, 236, 244, 246, 254, 256, 266, 268, 276, 278, 288, 294, 304, 308, 314, 318, 348, 358, 374

Offset

1,2

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

Table of n, a(n) for n=1..58.

Formula

a(n) = A007591(n-1) + 1 for n > 1. [corrected by Georg Fischer, Jun 20 2020]

Mathematica

Select[Range[0, 400, 2], PrimeQ[#^2-2#+5]&] (* Harvey P. Dale, Jan 04 2015 *)

Prog

(Magma) [n: n in [0..100]|IsPrime(n^2-2*n+5)] // Vincenzo Librandi, Nov 16 2010
(PARI) is(n)=isprime(n^2-2*n+5) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A005473 gives primes, A007591.

Sequence in context: A054409 A344001 A152973 * A274170 A367745 A173144

Adjacent sequences: A089744 A089745 A089746 * A089748 A089749 A089750

Keyword

nonn,easy

Author

Giovanni Teofilatto, Jan 08 2004

Status

approved