A110872 Numbers n such that (n^2+7)/8 is prime.

3, 7, 9, 15, 17, 23, 25, 33, 39, 41, 47, 55, 71, 81, 87, 89, 95, 103, 113, 121, 127, 129, 137, 143, 151, 153, 169, 177, 191, 193, 199, 201, 215, 223, 225, 263, 265, 271, 281, 297, 319, 327, 335, 337, 345, 351, 359, 369, 375, 401, 407, 415, 417, 423, 439, 447

Offset: 1

Author

Giovanni Teofilatto, Sep 18 2005

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A055469, A067186, A110873.

Programs

Mathematica

Select[Range[300], PrimeQ[(#^2 + 7)/8] &] (* Ray Chandler, Oct 08 2005 *)

PARI

is(n)=isprime((n^2+7)/8) \\ Charles R Greathouse IV, May 22 2017

Formula

a(n) = 2*A067186(n) + 1 = Sqrt(A110873(n)).

Extensions

Extended by Ray Chandler, Oct 08 2005