Some remarks on Ramanujan sums and cyclotomic polynomials.

link: http://arxiv.org/abs/1002.3221
Abstract

We investigate the polynomials $\sum_{k=0}^{n-1} c_n(k)x^k$ and
$\sum_{k=0}^{n-1} |c_n(k)| x^k$, where $c_n(k)$ denote the Ramanujan sums. We
point out connections and analogies to the cyclotomic polynomials.