2 2 1 3 3 1
3 $S$ has four subsequences: $(), (1), (3), (1, 3)$. $T$ has four subsequences: $(), (3), (1), (3, 1)$. There are $1 \times 1$ pair of subsequences in which the subsequences are both $()$, $1 \times 1$ pair of subsequences in which the subsequences are both $(1)$, and $1 \times 1$ pair of subsequences in which the subsequences are both $(3)$, for a total of three pairs.
2 2 1 1 1 1
6 $S$ has four subsequences: $(), (1), (1), (1, 1)$. $T$ has four subsequences: $(), (1), (1), (1, 1)$. There are $1 \times 1$ pair of subsequences in which the subsequences are both $()$, $2 \times 2$ pairs of subsequences in which the subsequences are both $(1)$, and $1 \times 1$ pair of subsequences in which the subsequences are both $(1,1)$, for a total of six pairs. Note again that we distinguish two subsequences if the sets of the indices of the removed elements are different, even if the subsequences are the same in content.
4 4 3 4 5 6 3 4 5 6
16
10 9 9 6 5 7 5 9 8 5 6 7 8 6 8 5 5 7 9 9 7
191
20 20 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
846527861 Be sure to print the number modulo $10^9+7$.
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