A071428 Numbers n such that x^n + x^(n-1) + x^(n-2) + ... + x + 1 is irreducible over GF(3).

4, 6, 16, 18, 28, 30, 42, 52, 78, 88, 100, 112, 126, 136, 138, 148, 162, 172, 196, 198, 210, 222, 232, 256, 268, 280, 282, 292, 316, 330, 352, 378, 388, 400, 448, 460, 462, 486, 508, 520, 556, 568, 570, 592, 606, 616, 630, 640, 652, 676, 690, 700, 738, 750

Offset

1,1

Comments

n such that n+1 is a prime with primitive root 3 (A019334 except for the first term). [Joerg Arndt, Jul 05 2011]

Links

Table of n, a(n) for n=1..54.

Prog

(PARI) for(n=2, 1000, if(polisirreducible(Mod(1, 3)*sum(e=0, n, x^e)), print1(n+1, ", "))) /* Joerg Arndt, Jul 05 2011 */
(PARI) forprime(p=5, 1000, if(znorder(Mod(3, p))==p-1, print1(p-1, ", "))) /* much faster */ /* Joerg Arndt, Jul 05 2011 */

Crossrefs

Cf. A071642.

Sequence in context: A056222 A186201 A138624 * A117988 A263636 A238411

Adjacent sequences: A071425 A071426 A071427 * A071429 A071430 A071431

Keyword

easy,nonn

Author

Robert G. Wilson v, Jun 22 2002

Status

approved