A239787 - OEIS

%I #14 Sep 08 2022 08:46:07

%S 1,2,4,6,10,14,26,34,36,40,44,54,64,66,70,84,86,92,100,102,116,122,

%T 134,146,150,152,156,160,172,174,176,180,190,194,200,216,252,254,262,

%U 274,306,320,322,334,336,350,352,374,384,402,414,440,442,444,460

%N Numbers n such that 3n^3 - 1 is prime.

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

%H Vincenzo Librandi, <a href="/A239787/b239787.txt">Table of n, a(n) for n = 1..1000</a>

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

%t Select[Range[1000], PrimeQ[3 #^3 - 1] &] (* _Vincenzo Librandi_, Mar 29 2014 *)

%o (Python)

%o import sympy

%o from sympy import isprime

%o {print(n) for n in range(10**3) if isprime(3*(n**3)-1)}

%o (PARI) s=[]; for(n=1, 1000, if(isprime(3*n^3-1), s=concat(s, n))); s \\ _Colin Barker_, Mar 27 2014

%o (Magma) [n: n in [0..1000] | IsPrime(3*n^3-1)]; // _Vincenzo Librandi_, Mar 29 2014

%Y Cf. A116954.

%K nonn,easy

%O 1,2

%A _Derek Orr_, Mar 26 2014