12. What is the sum of all possible $\binom{i}{j}$ subject to the restrictions that $i \geq 10$, $j \geq 0$, and $i+j \leq 20$? Count different $i, j$ that yield the same value separately - for example, count both $\binom{10}{1}$ and $\binom{10}{9}$.

Let's think step by step and output the final answer within \boxed{}.
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