A085900 Numbers k such that k-th cyclotomic polynomial has exactly 3 negative coefficients.

14, 15, 28, 30, 45, 56, 60, 75, 90, 98, 112, 120, 135, 150, 180, 196, 224, 225, 240, 270, 300, 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, 1792, 1800, 1875

Offset

0,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..96

Example

14 is a member because the 14th cyclotomic polynomial is P(x) = x^6-x^5+x^4-x^3+x^2-x+1 that has 3 negative coefficients. - Paolo P. Lava, Oct 26 2017

Maple

with(numtheory): P:=proc(n) local x;
if nops(select(x->x<0, [coeffs(cyclotomic(n, x))]))=3 then n; fi;
end: seq(P(j), j=1..1875); # Paolo P. Lava, Oct 26 2017

Mathematica

Select[Range@ 2000, Count[CoefficientList[Cyclotomic[#, x], x], _?(# < 0 &)] == 3 &] (* Michael De Vlieger, Oct 26 2017 *)

Crossrefs

Cf. A085459, A086780.

Sequence in context: A084429 A207036 A087430 * A075659 A022104 A041398

Adjacent sequences: A085897 A085898 A085899 * A085901 A085902 A085903

Keyword

nonn

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 16 2003

Extensions

More terms from Paolo P. Lava, Oct 26 2017

Status

approved