A110994 Numbers n such that 23*n^2 - 4 is prime.

1, 5, 7, 15, 21, 23, 27, 49, 63, 65, 83, 89, 103, 107, 131, 135, 149, 159, 161, 181, 187, 197, 203, 209, 223, 231, 237, 245, 253, 257, 261, 279, 281, 301, 307, 313, 327, 331, 335, 337, 369, 371, 377, 385, 397

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

If n=89 then 23*n^2 - 4 = 182179 (prime).

Maple

select(n -> isprime(23*n^2-4), [seq(i, i=1..1000, 2)]); # Robert Israel, Jul 04 2018

Mathematica

Select[Range[400], PrimeQ[(23#^2 - 4)] &] (* Stefan Steinerberger, Feb 28 2006 *)

Prog

(PARI) is(n)=isprime(23*n^2-4) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A314365 A314366 A068580 * A015833 A072022 A003429

Adjacent sequences: A110991 A110992 A110993 * A110995 A110996 A110997

Keyword

nonn,easy

Author

Parthasarathy Nambi, Sep 30 2005

Extensions

More terms from Stefan Steinerberger, Feb 28 2006

Status

approved