Xx2,X=xi+i2+…+i=yr r-combination ofs Definition 1: The generating function for the sequence a0s2a1y…,any… of real numbers is the infinite series f(X)=a0+a1x+a2x2+…+anx"+…, an ∑ax=∑ b,x' if only if a;=b; for all i=0,1,…n, i=0 i=0▪ x i1x i2…xik= xi1+i2+…+ik=xr ▪ r-combination of S ▪ Definition 1: The generating function for the sequence a0 ,a1 ,…,an ,… of real numbers is the infinite series f(x)=a0+a1x+a2x 2+…+anx n+…, and    =  = = 0 i 0 i i i i i a x b x if only if ai=bi for all i=0,1, …n, …