A138924 - OEIS

%I #21 Nov 11 2019 10:25:25

%S 3,4,6,8,9,11,14,15,21,24,25,31,42,43,45,47,58,59,77,107,124,142,144,

%T 177,192,254,279,360,407,437,480,525,542,551,579,764,811,822,891,917,

%U 1018,1028,1150,1326,1376,1464,1468,1650,1719,1924,2096,2098,2176,2226

%N Indices k such that A020505(k)=Phi[k](-6) is prime, where Phi is a cyclotomic polynomial.

%H Robert Price, <a href="/A138924/b138924.txt">Table of n, a(n) for n = 1..104</a>

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

%t Select[ Range[ 2000], PrimeQ[ Cyclotomic[#, -6]] &] (* _Robert G. Wilson v_, Mar 25 2012 *)

%o (PARI) for( i=1,999, ispseudoprime( polcyclo(i,-6)) && print1( i",")) /* use ...subst(polcyclo(i),x,-6)... in PARI < 2.4.2 */

%Y Cf. A020505, A138920-A138940.

%K nonn

%O 1,1

%A _M. F. Hasler_, Apr 03 2008

%E a(51)-a(54) from _Robert Price_, Apr 02 2012