Recently a constructive theory of pseudorandomness of binary sequences has been developed and many constructions for binary
sequences with strong pseudorandom properties have been given. In the applications one usually needs large families of binary
sequences of this type. In this paper we adapt the notions of collision and avalanche effect to study these pseudorandom properties
of families of binary sequences. We test two of the most important constructions for these pseudorandom properties, and it
turns out that one of the two constructions is ideal from this point of view as well, while the other construction does not
possess these pseudorandom properties.
In recent papers ,  I studied collision and avalanche effect in families of finite pseudorandom binary sequences.
Motivated by applications, Mauduit and Sárközy in  generalized and extended this theory from the binary case to k-ary sequences, i.e., to k symbols. They constructed a large family of k-ary sequences with strong pseudorandom properties. In this paper our goal is to extend the study of the pseudorandom properties
mentioned above to k-ary sequences. The aim of this paper is twofold. First we will extend the definitions of collision and avalanche effect to
k-ary sequences, and then we will study these related properties in a large family of pseudorandom k-ary sequences with “small” pseudorandom measures.
In an earlier paper we studied collisions and avalanche effect in two of the most important constructions given for large
families of binary sequences possessing strong pseudorandom properties. It turned out that one of the two constructions (which
is based on the use of the Legendre symbol) is ideal from this point of view, while the other construction (which is based
on the size of the modulo p residue of f(n) for some polynomial f(x) ∈
[x]) is not satisfactory since there are “many” collisions in it. Here it is shown that this weakness of the second construction
can be corrected: one can take a subfamily of the given family which is just slightly smaller and collision free.