Your $f(X)$ is$$\sum_{i=m}^\infty{i\choose m}\frac{X^{2i+1}}{(1-X)^{2i+2}}=\frac{X}{(1-X)^2}\frac{(X^2/(1-X)^2)^m}{(1-X^2/(1-X)^2)^{m+1}}$$(using the principle in your previous line). This simplifies to$$\frac{X^{2m+1}}{(1-2X)^{m+1}}.$$
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Your $f(X)$ is$$\sum_{i=m}^\infty{i\choose m}\frac{X^{2i+1}}{(1-X)^{2i+2}}=\frac{X}{(1-X)^2}\frac{(X^2/(1-X)^2)^m}{(1-X^2/(1-X)^2)^{m+1}}$$(using the principle in your previous line). This simplifies to$$\frac{X^{2m+1}}{(1-2X)^{m+1}}.$$