Which of these functions represents an arithmetic sequence?
f(n)=n2+1f(n) = n^2 + 1f(n)=n2+1
f(n)=2nf(n) = 2^nf(n)=2n
f(n)=4n−3f(n) = 4n - 3f(n)=4n−3
f(n)=1nf(n) = \frac{1}{n}f(n)=n1