math
posted by jesus gonzalez .
rewrite the series in sigma notation 4+16+64+...+256+1024

We note that the series is a geometric series with a common ratio of r=16/4=4
The first term, i=1, is given by
4=1*4^1=4^i
The second term, i=2, is given by
16=4^2=4^i
...
and the last term, i=5, is given by
1024=4^5=4^i
Therefore the summation is for
4^i for i=1 to i=5.