The value of \( \sum_{\substack{r=0}}^{s} \sum_{\substack{s=1 \\ r \leq s}}^{n} C_{s}^{s} C_{r} ...
The value of \( \sum_{\substack{r=0}}^{s} \sum_{\substack{s=1 \\ r \leq s}}^{n} C_{s}^{s} C_{r} \) is
(a) \( 3^{n}-1 \)
(b) \( 3^{n}+1 \)
(c) \( 3^{n} \)
(d) \( 3\left(3^{n}-1\right) \)
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