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A200906 Numbers n such that cyclotomic polynomial value Phi(5,n!) is prime. 13

%I

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

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

%C 2415 corresponds to a probable prime. - _Serge Batalov_, Nov 24 2011

%C a(12) > 15000. - _Robert Price_, Jun 20 2015

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

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

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

%Y Cf. A002981, A002982, A046029, A046029.

%K nonn

%O 1,3

%A _Serge Batalov_, Nov 23 2011

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Last modified November 22 13:47 EST 2019. Contains 329393 sequences. (Running on oeis4.)