OFFSET
1,1
COMMENTS
Most terms of this sequence are multiples of 3, exceptions are 20, 59, 91, 152, 223, 232, 340, 380, 533, 547, 773... corresponding to a(n) with n=5, 9, 11, 12, 14, 15, 18, 19, 22, 24, 31...
LINKS
Robert Price, Table of n, a(n) for n = 1..68
Yves Gallot, Cyclotomic polynomials and prime numbers
MATHEMATICA
Select[Range[1000], PrimeQ[Cyclotomic[#, -9]] &]
PROG
(PARI) for( i=1, 999, ispseudoprime( polcyclo(i, -9)) && print1( i", ")) /* use ...subst(polcyclo(i), x, -9)... in PARI < 2.4.2 */
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Apr 03 2008
EXTENSIONS
a(32)-a(51) by Robert Price, Mar 22 2012
STATUS
approved