Example :

There are 21 possible combinations (with repeats) of two things for any six objects (e.g. a, b, c, d, e, f). They are as follows:
aa ab ac ad ae af bb bc bd be bf cc cd ce cf dd de df ee ef ff
This computation is presented in cell A2 of the sample spreadsheet below.
The spreadsheet example below also illustrates how to use the Combina function to determine the number of combinations (with repeats) for different numbers of objects from a set of six.