A138923 Indices k such that A020506(k)=Phi[k](-7) is prime, where Phi is a cyclotomic polynomial.

3, 9, 10, 15, 17, 23, 25, 26, 27, 28, 29, 36, 42, 47, 48, 61, 76, 84, 110, 126, 148, 210, 224, 262, 280, 288, 296, 298, 325, 327, 332, 352, 365, 456, 513, 528, 740, 1062, 1162, 1445, 1460, 1518, 1619, 1660, 2094, 2130, 2260, 2380, 3398, 3447, 3918

Offset

1,1

Comments

There are only 6 terms between 365 and 1445 (exclusive).

Links

Robert Price, Table of n, a(n) for n = 1..97

Yves Gallot, Cyclotomic polynomials and prime numbers

Mathematica

Select[ Range[ 2400], PrimeQ[ Cyclotomic[#, -7]] &] (* Robert G. Wilson v, Mar 25 2012 *)

Prog

(PARI) for( i=1, 999, ispseudoprime( polcyclo(i, -7)) && print1( i", ")) /* use ...subst(polcyclo(i), x, -7)... in PARI < 2.4.2 */

Crossrefs

Cf. A020506, A138920-A138940.

Sequence in context: A030608 A118515 A191339 * A324584 A325284 A049096

Adjacent sequences: A138920 A138921 A138922 * A138924 A138925 A138926

Keyword

nonn

Author

M. F. Hasler, Apr 03 2008

Status

approved