ELI5 the formula to figure out all possible combinations without repeating any items but no upper or lower limit of the number to include. Order does not matter.
$\endgroup$ 61 Answer
$\begingroup$You can pick up $k$ items out of $100$ where $k=0,1,2,\ldots ,100$
Hence, all the possibilities are:
$$\sum_{k=0}^{100} \binom{100}{k}=2^{100}$$
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