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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS 2415 corresponds to a probable prime. - Serge Batalov, Nov 24 2011 a(12) > 15000. - Robert Price, Jun 20 2015 LINKS 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

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Last modified October 21 04:26 EDT 2019. Contains 328291 sequences. (Running on oeis4.)