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A071428
Numbers n such that x^n + x^(n-1) + x^(n-2) + ... + x + 1 is irreducible over GF(3).
0
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]
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
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Jun 22 2002
STATUS
approved