Let f:(0, ∞) → R and F (x)=∫_0^x t f(t) dt. If F (x^2)=x^4+x^5, then Σ_r =1^12 f( r^2) is equal to ____.

Let $\displaystyle f:(0, \infty) \rightarrow \mathbf{R}$ and $\displaystyle \mathrm{F}(x)=\int_0^x \mathrm{t} f(t) \mathrm{dt}$. If $\displaystyle \mathrm{F}\left(x^2\right)=x^4+x^5$, then $\displaystyle \sum_{\mathrm{r}=1}^{12} f\left(\mathrm{r}^2\right)$ is equal to $\displaystyle \_\_\_\_$.