What is the generating function for the sequence an=na_n = nan=n?
x(1−x)2\frac{x}{(1-x)^2}(1−x)2x
1(1−x)2\frac{1}{(1-x)^2}(1−x)21
x1−x2\frac{x}{1-x^2}1−x2x
x2(1−x)2\frac{x^2}{(1-x)^2}(1−x)2x2