Central term in the S000845(n)-th cyclotomic polynomial.
1, -3, 5, -7, 19, 25, 27, 45, 349, 393, 30921, 43927, -53045, 14014017
1
T. D. Noe, Plot of 14 terms
Andrew Arnold, A high-performance algorithm for calculating cyclotomic polynomials, 2010.
Andrew Arnold and Michael Monagan, Calculating cyclotomic polynomials, 2011.
(Mma) t = {{0,1}}; mx = 1; Do[If[Union[Transpose[FactorInteger[n]][[2]]] == {1}, c = CoefficientList[Cyclotomic[n, x], x]; q = c[[1 + EulerPhi[n]/2]]; If[Abs[q] > mx, mx = Abs[q]; AppendTo[t, {n, q}]]], {n, 3, 40755, 2}]; Abs[Transpose[t][[2]]]
Cf. S000845.
sign,hard
T. D. Noe, Feb 08 2016