Almost perfect binary functions (Q2366273)

In [IEEE Trans. Inf. Theor. 38, 1412-1418 (1992)], \textit{J. Wolfmann} defined almost perfect binary sequences as periodic sequences of \(+1\)'s and \(-1\)'s so that all except one of their out-of-phase autocorrelation coefficients are zero. Wolfmann studied such sequences by using properties of the ring \(F_ 2[x]/(x^ n-1)\). In this paper the author uses the arithmetic of cyclotomic fields to solve a number of problems raised in Wolfmann's paper.