

A086761


Numbers n such that nth cyclotomic polynomial has exactly 5 nonzero terms.


2



5, 10, 20, 25, 40, 50, 80, 100, 125, 160, 200, 250, 320, 400, 500, 625, 640, 800, 1000, 1250, 1280, 1600, 2000, 2500, 2560, 3125, 3200, 4000, 5000, 5120, 6250, 6400, 8000, 10000, 10240, 12500, 12800, 15625, 16000, 20000, 20480, 25000, 25600, 31250, 32000
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OFFSET

1,1


COMMENTS

A206787(a(n)) = 6. [Reinhard Zumkeller, Feb 12 2012]
All terms have the form 2^a 5^b with a >= 0 and b > 0.  T. D. Noe, Feb 13 2012


LINKS

Table of n, a(n) for n=1..45.


MATHEMATICA

Select[Range[1000], Count[CoefficientList[Cyclotomic[#, x], x], 0] == EulerPhi[#]  4 &] (* T. D. Noe, Feb 13 2012 *)


CROSSREFS

Cf. A051664, A065119.
Sequence in context: A245387 A115799 A072703 * A045191 A065958 A065969
Adjacent sequences: A086758 A086759 A086760 * A086762 A086763 A086764


KEYWORD

nonn


AUTHOR

Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 02 2003


EXTENSIONS

More terms from T. D. Noe, Feb 13 2012


STATUS

approved



