A176547 Numbers n such that 2*n^2 + 6*n + 1 is prime.

3, 6, 15, 18, 21, 24, 27, 33, 57, 60, 63, 66, 75, 78, 87, 90, 96, 108, 111, 117, 129, 138, 141, 144, 147, 153, 159, 165, 168, 171, 180, 186, 189, 201, 204, 222, 228, 231, 234, 237, 243, 246, 249, 252, 255, 258, 264, 273, 294, 309, 312, 315, 321, 339, 348, 351

Offset

1,1

Comments

Conjecture: If p=2*n^2+6*n+1 is prime then 2^p-1 is not prime.

Tested for all p < 24036583 = A000043(41). - Joerg Arndt, Oct 06 2012

Links

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

Example

For n=3, p=37 and 2^37-1 = 223 * 616318177.

Mathematica

Select[Range[500], PrimeQ[2 #^2 + 6 # + 1] &] (* Vincenzo Librandi, Oct 08 2012 *)

Prog

(Magma) [n: n in [1..1000]| IsPrime(2*n^2 + 6*n + 1)];
(PARI) is(n)=isprime(2*n^2+6*n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A310124 A059969 A224864 * A310125 A124518 A160724

Adjacent sequences: A176544 A176545 A176546 * A176548 A176549 A176550

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 20 2010

Status

approved