Math Help - Series and Sequences

1. Series and Sequences

Ok, first a really simple sequence, but for some reason this online page isn't accepting it.

Find a formula for the general term an of the sequence, assuming that the pattern of the first few terms continues.

I'm putting in 5/(4^n) but it's not taking it. Either this input is messed up, or i'm missing something elementary.

2. Try $a_n=\displaystyle\frac{5}{4^{n-1}}$.

3. Ahh, yes. I was assuming n=0, but I guess I shouldn't assume anything