a researcher sets out to measure drug use on US college campuses by asking a representative sample of undergraduates whether they are currently receiving federal grants or loans. What is the problem with this measure?

Given that the sequence is:
1,2,4,8,32
the recursive formula will be found as follows:
first term is=1
the sequence can be written as:
1,2,4,8,32
=(1*2^0),(1*2^1),(1*2^2),(1*2^3),(1*2^4)
thus the recursive formula will be
an=a1(r)^(n-1)
plugging the values we get:
an=1(2)^(n-1)