OFFSET
1,1
COMMENTS
When n is prime, then the solutions are given in A088790.
No term of this sequence is congruent to 1 mod 4. In general, if k = s^2*t where t is squarefree and t == 1 (mod 4), then Cyclotomic(k,t*x^2) is the product of two polynomials. See the Wikipedia link below. - Jianing Song, Sep 25 2019
All terms <= 1858 have been proven with PARI's implementation of ECPP. All larger terms are BPSW PRPs. There are no further terms <= 30000. - Lucas A. Brown, Dec 28 2020
LINKS
Eric Weisstein's World of Mathematics, Cyclotomic Polynomial
Wikipedia, Aurifeuillean factorization
MATHEMATICA
Do[s=Cyclotomic[n, n]; If[PrimeQ[s], Print[n]], {n, 2, 256}]
PROG
(PARI) for(n=2, 10^9, if(ispseudoprime(polcyclo(n, n)), print1(n, ", "))); \\ Joerg Arndt, Jan 22 2015
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Labos Elemer, May 02 2002
EXTENSIONS
More terms from T. D. Noe, Oct 17 2003
a(29) from Charles R Greathouse IV, May 05 2011
STATUS
approved