Total Number of all r-Combinations of n Objects.
— Suppose all the combinations of
n objects taken one at a time (the
number of the objects) are found, and then all the combinations taken two at a time, then all those three at a
so on until all those taken n
at a time (all at once) are formed. How many
combinations will there be
— J.E. Thompson, Algebra for the Practical Man (D. Van