Or one over one minus Z times, log one minus Z, we get the generating function for the harmonic numbers, a harmonic numbers is sum from, of K goes from one to N of one over one mine, one over K. and we saw that the harmonic numbers, arose in the analysis of quick sort and naturally arise in many places in the analysis of algorithms and now we have, we can represent'em with that single function, one over one minus Z, natural log of, one over one minus Z. and that partial sum idea, generalizes to the idea of a c onvolution. if you have, any two generating functions, you can multiply them together. and you get the, generating function for this, convolved product. sum from where the nth term in the sequence is sum from zero goes from k to n of akbn-k. 