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A138922 Indices k such that A020507(k)=Phi[k](-8) is prime, where Phi is a cyclotomic polynomial. 1
6, 15, 18, 21, 39, 69, 159, 165, 174, 231, 378, 408, 501, 504, 606, 873, 897, 1122, 1209, 1395, 1947, 2040, 2361, 2778, 3369, 7305, 7647, 8154, 8331, 9483, 13071, 14616, 15819, 20301, 21282, 27144, 31083, 34725, 35775, 36855, 38118, 39360 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..42.

Yves Gallot, Cyclotomic polynomials and prime numbers

MATHEMATICA

Select[Range[1000], PrimeQ[Cyclotomic[#, -8]] &]

PROG

(PARI) for( i=1, 999, ispseudoprime( polcyclo(i, -8)) && print1( i", ")) /* use ...subst(polcyclo(i), x, -8)... in PARI < 2.4.2 */

CROSSREFS

Cf. A020507, A138920-A138940.

Sequence in context: A070999 A128693 A105285 * A044058 A105139 A002599

Adjacent sequences:  A138919 A138920 A138921 * A138923 A138924 A138925

KEYWORD

nonn,more

AUTHOR

M. F. Hasler, Apr 03 2008

EXTENSIONS

a(18)-a(42) from Robert Price, Mar 25 2012

STATUS

approved

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Last modified August 25 21:00 EDT 2019. Contains 326324 sequences. (Running on oeis4.)