A100331 Positive integers n such that n^6 + n^5 + n^4 + n^3 + n^2 + n - 1 is prime.

1, 3, 9, 15, 18, 20, 28, 33, 55, 65, 68, 84, 88, 98, 109, 115, 119, 120, 124, 129, 134, 135, 140, 159, 165, 173, 185, 188, 190, 205, 223, 239, 264, 270, 275, 278, 288, 295, 305, 308, 323, 329, 350, 368, 370, 388, 409, 460, 464, 499, 510, 525, 540, 565, 579, 593

Offset: 1

Author

Ray G. Opao, Nov 16 2004

Keywords

• nonn
• easy

Examples

			3 is in the sequence because 3^6 + 3^5 + 3^4 + 3^3 + 3^2 + 3 - 1 = 1091, which is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A100330.

Programs

Magma

[n: n in [0..700] | IsPrime(n^6+n^5+n^4+n^3+n^2+n-1)]; // Vincenzo Librandi, Dec 13 2015

Maple

A100331:=n->`if`(isprime(-1+add(n^i, i=1..6)), n, NULL): seq(A100331(n), n=1..1000); # Wesley Ivan Hurt, Dec 13 2015

Mathematica

Select[Range[600], PrimeQ[Sum[ #^i, {i, 6}] - 1] &] (* Ray Chandler, Nov 17 2004 *)

PARI

is(n) = ispseudoprime(n^6+n^5+n^4+n^3+n^2+n-1) \\ Altug Alkan, Dec 13 2015