Let t n = (−1) s 2 (n) , where s 2 (n) is the sum of binary digits function. The sequence (t n ) n∈N is the well-known Prouhet-Thue-Morse sequence. In this note we initiate the study of the sequence (h n ) n∈N , where h 0 = 0, h 1 = 1 and for n ≥ 2 we define h n recursively as follows:We prove several results concerning arithmetic properties of the sequence (h n ) n∈N . In particular, we prove non-vanishing of h n for n ≥ 5, automaticity of the sequence (h n (mod m)) n∈N for each m, and other results.