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If some or all of n objects are taken at...

If some or all of n objects are taken at a time, then the number of combinations is `2^(n) - 1`.

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If some or all objects taken at a time, then number of selection would be
`""^(n)C_(1) + ""^(n)C_(2) + ""^(n)C_(3) + … + ""^(n)C_(n) = 2^(n) - 1" " [because ""^(n)C_(0) + ""^(n)C_(1) + ""^(n)C_(2) + … + ""^(n)C_(n) = 2^(n)]`
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