A086779 Numbers k such that k-th cyclotomic polynomial has exactly 7 nonzero terms.

7, 14, 15, 28, 30, 45, 49, 56, 60, 75, 90, 98, 112, 120, 135, 150, 180, 196, 224, 225, 240, 270, 300, 343, 360, 375, 392, 405, 448, 450, 480, 540, 600, 675, 686, 720, 750, 784, 810, 896, 900, 960, 1080, 1125, 1200, 1215, 1350, 1372, 1440, 1500, 1568, 1620

Offset

1,1

Links

Table of n, a(n) for n=1..52.

Formula

{n: A051664(n)=7}. - R. J. Mathar, Sep 15 2012

Mathematica

Select[Range[2000], Count[CoefficientList[Cyclotomic[#, x], x], 0] == EulerPhi[#] - 6 &] (* T. D. Noe, Feb 13 2012 *)

Prog

(PARI) isok(n) = {my(p = polcyclo(n)); #select(x->x, vector(1+poldegree(p), k, polcoeff(p, k-1))) == 7; } \\ Michel Marcus, Oct 26 2017

Crossrefs

Cf. A086761.

Sequence in context: A062056 A173024 A115770 * A269173 A167197 A336797

Adjacent sequences: A086776 A086777 A086778 * A086780 A086781 A086782

Keyword

nonn

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 03 2003

Extensions

Extended by T. D. Noe, Feb 13 2012

Status

approved