xN = f(x1,x2,x3,...,xN-1)
This is a sequence of numbers which is determinable.
That is the next number in the sequence can be determined if the previous numbers are given and the function of f( ) is known.

The collection of data may not be necessary.

If for instance N = 2

then x2 = f(x1)

and x3 = f(x1,x2,x3)

x4 = f(x1, x2, x3)

This can be repeated for x5, x6, x7, .... xJ.

I would be interested in knowing if the author had a different intended meaning.