A111148 Numbers n such that 5*n^2 + 4 is prime.

9, 15, 33, 51, 57, 99, 111, 117, 135, 141, 183, 189, 195, 267, 309, 327, 345, 369, 387, 399, 405, 411, 429, 441, 447, 495, 513, 525, 537, 567, 603, 609, 645, 663, 681, 687, 705, 723, 777, 783, 789, 807, 813, 831, 861, 897, 909, 915, 981

Offset

1,1

Links

Table of n, a(n) for n=1..49.

Example

If n=399 then 5*n^2 + 4 = 796009 (prime).

Mathematica

Select[Range[1000], PrimeQ[5*#^2 + 4] &] (* Stefan Steinerberger, Feb 26 2006 *)

Prog

(PARI) is(n)=isprime(5*n^2+4) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A107076 A155775 A228096 * A125216 A058505 A133763

Adjacent sequences: A111145 A111146 A111147 * A111149 A111150 A111151

Keyword

nonn,easy

Author

Parthasarathy Nambi, Oct 18 2005

Extensions

More terms from Stefan Steinerberger, Feb 26 2006

Status

approved