A138937 Indices k such that A019325(k)=Phi[k](7) is prime, where Phi is a cyclotomic polynomial.

5, 6, 13, 18, 21, 28, 30, 34, 36, 46, 48, 50, 54, 55, 58, 63, 76, 84, 94, 105, 122, 131, 148, 149, 224, 280, 288, 296, 332, 352, 456, 528, 531, 581, 650, 654, 730, 740, 759, 1026, 1047, 1065, 1460, 1660, 1699, 1959, 2067, 2260, 2380, 2665, 2890, 3238, 4020

Offset: 1

Author

M. F. Hasler, Apr 03 2008

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..95
• Yves Gallot, Cyclotomic polynomials and prime numbers
• Index entries for cyclotomic polynomials, values at X

Crossrefs

Cf. A019325, A138920-A138940.

Programs

Mathematica

Select[Range[1000], PrimeQ[Cyclotomic[#, 7]] &]

PARI

for( i=1,999, ispseudoprime( polcyclo(i,7)) && print1( i",")) /* use ...subst(polcyclo(i),x,7)... in PARI < 2.4.2 */

Extensions

a(40)-a(53) from Robert Price, Apr 18 2012