In a series of papers Mauduit and Sárközy studied finite pseudorandom sequences. In particular, in Part I they showed that the Legendre symbol forms an 'ideally good' pseudorandom sequence. In other parts of the series numerous other binary sequences have been tested for pseudorandomness but neither of them proved to be as 'good' as the Legendre symbol. Here another 'very good' sequence is constructed by using the notion of index.