Let S be a set of n consecutive natural numbers.

How to find the number of ordered pairs (A,B), where A and B are subsets of S and A is a proper subset of B?

For Example:

Let the set S = {1, 2, 3, 4, 5, 6, 7, 8}.

Find the number of ordered pairs (A, B), where A and B are subsets of S and A is a proper subset of B.

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