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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
OFFSET
1,1
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
KEYWORD
nonn,more
AUTHOR
M. F. Hasler, Apr 03 2008
EXTENSIONS
a(18)-a(42) from Robert Price, Mar 25 2012
STATUS
approved