Let ${Phi}_n(x)={sum}^{{phi}(n)}_{k=0}a(n,k)x^k$ denote the n-th cyclotomic polynomial. In this note, let p < q < r be odd primes, where $q{ ot{equiv}}1$ (mod p) and $r{equiv}-2$ (mod pq), we construct an explicit k such that a(pqr, k) = -2.