We know that a geometric sequence is given by:
where r is the common ratio of the sequence.
For this sequence we have that the common ratio is r=2, this comes from the fact that in the first day we have 6 dots, for the second day we have twelve and for the third day we have 24. We also notice that the first term is:
Therefore the sequence is given by:
Now, to find the zeoth term we plug n=0 in the sequence above, therefore the zeroth term is: