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 A085900 Numbers k such that k-th cyclotomic polynomial has exactly 3 negative coefficients. 1
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified June 9 11:04 EDT 2023. Contains 363178 sequences. (Running on oeis4.)