A247350 - OEIS

%I #15 Sep 28 2014 19:57:09

%S 1,2,3,4,5,7,8,12,14,15,17,22,28,33,35,39,40,45,53,57,58,59,65,70,73,

%T 74,77,80,82,83,85,93,97,99,100,102,103,104,107,115,117,118,122,128,

%U 134,139,142,143,148,152,159,164,173,178,182,184,185,188,190,195,198

%N Numbers x such that 8*x^3 - 8*x^2 + 4*x + 1 is prime.

%C Since 8*x^3 - 8*x^2 + 4*x + 1 = (2*x-1)^3 + (2x-1)^2 + (2x-1) + 2, the corresponding primes are of the form k^3 + k^2 + k + 2 and are in A088547.

%H Jens Kruse Andersen, <a href="/A247350/b247350.txt">Table of n, a(n) for n = 1..10000</a>

%F 8*a(n)^3 - 8*a(n)^2 + 4*a(n) + 1 = A088547(n+1).

%t Select[Range[1000], PrimeQ[1 + 4*# - 8*#^2 + 8*#^3] &]

%o (PARI) is(n)=isprime(8*n^3-8*n^2+4*n+1)

%Y Cf. A088547 (primes of form k^3+k^2+k+2).

%K nonn

%O 1,2

%A _Jean-Christophe Hervé_, Sep 17 2014