Logarthim - Finding expression - URGENT PLZZ

log[base2]8, log[base4]8, log[base8]8, log[base18, log[base32]8, log[base64]8,

I am given this sequence and i need to find an expression for the nth term in form of p/q, where p and q belongs to z(integer).

i guess it has to do with the bases

like log[base2]8

= log8/log2

= log8 - log2

= ??????

then how to find an expression

I tried the following:

1) since the bases form a geometric progression

i found the common ratio

which is r =Un/Un-1

ex: 8/4 = 2

2) The nth term formula for a geometric progression

is Un= ar^(n-1)

where a = 1st term, which is Log(base2)8

r=common ratio, which is 2

n=the rank

so the expression is

Un= Log(base2)8(2)^n-1

However its not quite correct

beacuse if we tested it, when n=7

to complete the sequence

the value should be log(base128)8

NOT Log(base2)8 x 128

I hope you get where i am going

I really appreciate ypu help

THANK YOU!!!!!!