A028879 Numbers k such that k^2 - 6 is prime.

3, 5, 7, 13, 17, 23, 25, 47, 53, 55, 65, 67, 73, 77, 83, 85, 97, 107, 113, 115, 125, 133, 143, 145, 155, 167, 187, 193, 197, 203, 205, 215, 235, 263, 275, 293, 317, 323, 325, 343, 355, 367, 373, 377, 383, 395, 415, 457, 463, 467, 475, 487, 503, 505, 533, 545

Offset: 1

Author

Patrick De Geest

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000
• Patrick De Geest, Palindromic Quasipronics of the form n(n+x)

Programs

Magma

[n: n in [3..1000] |IsPrime(n^2 - 6 )]; // Vincenzo Librandi, Nov 19 2010

Mathematica

Select[Range[3, 500], PrimeQ[#^2 - 6] &] (* G. C. Greubel, Aug 19 2017 *)

PARI

is(n)=isprime(n^2-6) \\ Charles R Greathouse IV, May 22 2017

Formula

a(n) = sqrt(A028880(n)+6). - Zak Seidov, Mar 10 2015