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A258357
Numbers n such that cyclotomic polynomial value Phi(7,n!) is prime.
1
0, 1, 2, 3, 13, 470, 2957
OFFSET
1,3
COMMENTS
Except for the values 0,1,2 and 3, terms correspond to probable primes.
a(8) > 6502.
Also, numbers n such that n! belongs to A100330. - Michel Marcus, May 30 2015
EXAMPLE
3 is in the sequence because Phi(7,3!) = 1 + 6 + 6^2 + 6^3 + 6^4 + 6^5 + 6^6 = 55987 is prime.
MATHEMATICA
Select[Range[0, 6502], PrimeQ[Cyclotomic[7, #!]] &]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, May 27 2015
STATUS
approved