Answering a Question of Pott on Almost Perfect Sequences

Periodic binary (plus-minus) sequences all but one of whose out-of-phase autocorrelation coefficients are zero are studied by Wolfman [6]. Using the equivalence of these almost perfect sequences to certain cyclic divisible difference sets (noted by Bradley and Pott [1]), we settle the existence status of a perviously open case of an almost perfect sequence of length 852, thereby answering a question of Pott [5] negatively.