A239787 Numbers n such that 3n^3 - 1 is prime.

1, 2, 4, 6, 10, 14, 26, 34, 36, 40, 44, 54, 64, 66, 70, 84, 86, 92, 100, 102, 116, 122, 134, 146, 150, 152, 156, 160, 172, 174, 176, 180, 190, 194, 200, 216, 252, 254, 262, 274, 306, 320, 322, 334, 336, 350, 352, 374, 384, 402, 414, 440, 442, 444, 460

Offset: 1

Author

Derek Orr, Mar 26 2014

Keywords

• nonn
• easy

Comments

All the numbers in this sequence, excluding a(1), are even.

Examples

			3*2^3 - 1 = 23 is prime. Thus, 2 is a member of this sequence.
		

Links

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

Crossrefs

Cf. A116954.

Programs

Magma

[n: n in [0..1000] | IsPrime(3*n^3-1)]; // Vincenzo Librandi, Mar 29 2014

Mathematica

Select[Range[1000], PrimeQ[3 #^3 - 1] &] (* Vincenzo Librandi, Mar 29 2014 *)

PARI

s=[]; for(n=1, 1000, if(isprime(3*n^3-1), s=concat(s, n))); s \\ Colin Barker, Mar 27 2014

Python

import sympy
from sympy import isprime
{print(n) for n in range(10**3) if isprime(3*(n**3)-1)}