HMMT November 2011 H5
- Theme
- Answer
For any finite sequence of positive integers , let be the number of strictly increasing subsequences in with length 2 or more. For example, in the sequence , there are five increasing sub-sequences: , and , so . In an eight-player game of Fish, Joy is dealt six cards of distinct values, which she puts in a random order from left to right in her hand. Determine
where the sum is taken over all possible orders of the card values.
Dataset text NuminaMath olympiads. Quoted with source.
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