A138928 Indices n such that A020501(n) = phi(n)(-2) is prime, where Phi is a cyclotomic polynomial.

3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 24, 26, 30, 31, 32, 34, 38, 39, 40, 43, 45, 49, 54, 56, 61, 62, 63, 66, 75, 79, 80, 85, 87, 98, 101, 117, 120, 122, 127, 130, 138, 154, 161, 167, 170, 178, 183, 184, 186, 187, 191, 192, 199, 205, 207, 208

Offset

1,1

Comments

While the sequence is not very interesting up to a(n)<300, there are only 4 values in the interval [400,599].

Links

Robert Price, Table of n, a(n) for n = 1..227

Yves Gallot, Cyclotomic polynomials and prime numbers

Index entries for cyclotomic polynomials, values at X

Mathematica

Select[ Range[3, 1000], PrimeQ[ Cyclotomic[#, -2]] &] (* Robert G. Wilson v, Mar 25 2012 *)

Prog

(PARI) for( i=1, 999, isprime( polcyclo(i, -2)) && print1( i", ")) /* for PARI < 2.4.2 use ...subst(polcyclo(i), x, -2)...*/

Crossrefs

Cf. A020501, A138920-A138940.

Sequence in context: A329254 A359003 A183296 * A116587 A057903 A247833

Adjacent sequences: A138925 A138926 A138927 * A138929 A138930 A138931

Keyword

nonn

Author

M. F. Hasler, Apr 03 2008

Status

approved