A171140 Numbers k such that 6*k + 7 = p^2 (p=prime).

3, 7, 19, 27, 47, 59, 87, 139, 159, 227, 279, 307, 367, 467, 579, 619, 747, 839, 887, 1039, 1147, 1319, 1567, 1699, 1767, 1907, 1979, 2127, 2687, 2859, 3127, 3219, 3699, 3799, 4107, 4427, 4647, 4987, 5339, 5459, 6079, 6207, 6467, 6599, 7419, 8287, 8587

Offset: 1

Author

Vincenzo Librandi, Dec 04 2009

Keywords

• nonn
• easy

Comments

Subsequence of A164097. - R. J. Mathar, Jul 06 2010

Examples

			6*3  + 7 =  5^2, so  3 is a term;
6*7  + 7 =  7^2, so  7 is a term;
6*19 + 7 = 11^2, so 19 is a term;
6*27 + 7 = 13^2, so 27 is a term.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A164097.

Programs

Magma

[(p^2-7)/6: p in PrimesInInterval(4, 250)]; // Vincenzo Librandi, Apr 06 2013

Mathematica

Select[Range[10000], PrimeQ[Sqrt[6 # + 7]]&] (* Vincenzo Librandi, Apr 06 2013 *)