Hi. I look at the journal of Hosking in proving the properties of ARFIMA (0,d,0). It says there, when d < 1/2, the power series expansion of (1-z)^(-d) converges for absolute value of z less than 1 and thus stationary. can anyone help me how to show this one? I just forgot how to solve for a power series expansion and now, i don't know how .