A138921 Indices k such that A020508(k)=Phi[k](-9) is prime, where Phi is a cyclotomic polynomial.
3, 9, 12, 15, 20, 27, 33, 36, 59, 69, 91, 152, 207, 223, 232, 264, 336, 340, 380, 381, 492, 533, 540, 547, 549, 585, 615, 624, 627, 720, 773, 1009, 1287, 1320, 1428, 1537, 1823, 2093, 2401, 2724, 2733, 2804, 2920, 3316, 3803, 4124, 4132, 4620, 7143, 7520, 7708
Offset: 1
Keywords
Links
- Robert Price, Table of n, a(n) for n = 1..68
- Yves Gallot, Cyclotomic polynomials and prime numbers
Programs
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Mathematica
Select[Range[1000], PrimeQ[Cyclotomic[#, -9]] &]
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PARI
for( i=1,999, ispseudoprime( polcyclo(i,-9)) && print1( i",")) /* use ...subst(polcyclo(i),x,-9)... in PARI < 2.4.2 */
Extensions
a(32)-a(51) by Robert Price, Mar 22 2012
Comments