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 A138938 Indices k such that A019326(k)=Phi[k](8) is prime, where Phi is a cyclotomic polynomial. 2

%I

%S 1,3,9,30,42,78,87,138,189,303,318,330,408,462,504,561,1002,1389,1746,

%T 1794,2040,2418,2790,3894,4077,4722,6738,10641,14610,14616,15294,

%U 16662,18966,19059,26142,27144,28299,31638,33639,39360

%N Indices k such that A019326(k)=Phi[k](8) is prime, where Phi is a cyclotomic polynomial.

%H Yves Gallot, <a href="http://yves.gallot.pagesperso-orange.fr/papers/cyclotomic.html">Cyclotomic polynomials and prime numbers</a>

%H <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a>

%t Select[Range[1000], PrimeQ[Cyclotomic[#, 8]] &]

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

%Y Cf. A019326, A138920-A138940.

%K nonn

%O 1,2

%A _M. F. Hasler_, Apr 03 2008

%E a(17)-a(40) from _Robert Price_, Apr 20 2012

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Last modified May 26 18:08 EDT 2020. Contains 334630 sequences. (Running on oeis4.)