A200906 Numbers n such that cyclotomic polynomial value Phi(5,n!) is prime.

0, 1, 2, 4, 5, 21, 44, 64, 244, 268, 2415

Offset

1,3

Comments

2415 corresponds to a probable prime. - Serge Batalov, Nov 24 2011

a(12) > 15000. - Robert Price, Jun 20 2015

Links

Table of n, a(n) for n=1..11.

Example

5 is in the sequence because Phi(5,5!) = ((5!)^5-1)/(5!-1)= 209102521 is prime.

Mathematica

Do[If[PrimeQ[Cyclotomic[5, n!]], Print[n]], {n, 0, 600}]

Prog

(PARI) for(n=0, 600, x=n!; if(isprime(eval(polcyclo(5))), print(n)))

Crossrefs

Cf. A002981, A002982, A046029, A046029.

Sequence in context: A084592 A101587 A277853 * A036986 A144420 A126667

Adjacent sequences: A200903 A200904 A200905 * A200907 A200908 A200909

Keyword

nonn

Author

Serge Batalov, Nov 23 2011

Status

approved