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Reciprocal cyclotomic polynomials

Let $Ψ_n(x)$ be the monic polynomial having precisely all non-primitive $n$th roots of unity as its simple zeros. One has $Ψ_n(x)=(x^n-1)/Φ_n(x)$, with $Φ_n(x)$ the $n$th cyclotomic polynomial. The coefficients of $Ψ_n(x)$ are integers that like the coefficients of $Φ_n(x)$ tend to be surprisingly small in absolute value, e.g. for $n<561$ all coefficients of $Ψ_n(x)$ are $\le 1$ in absolute value. We establish various properties of the coefficients of $Ψ_n(x)$.