Answer
Yes, harmonic.
Work Step by Step
We are given:
$1, \frac{3}{5}, \frac{3}{7}, \frac{1}{3}$ ...
$\frac{1}{1}, \frac{3}{5}, \frac{3}{7}, \frac{1}{3}$ ...
We take the reciprocals of the terms:
$\frac{1}{1}, \frac{5}{3}, \frac{7}{3}, \frac{3}{1}$ ...
$1, 1.\overline 6, 2.\overline 3, 3$
We see that the terms increase by $0.6\overline 6$, or $\frac{2}{3}$. Thus the reciprocals form an arithmetic sequence, which implies that the original sequence is harmonic.