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A200906
Numbers n such that cyclotomic polynomial value Phi(5,n!) is prime.
13
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
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
KEYWORD
nonn
AUTHOR
Serge Batalov, Nov 23 2011
STATUS
approved