108. Unique Square. What square is equal to the product of four consecutive odd numbers?
108. If $n(n+2)(n+4)(n+6)=m^{2}$, then $\left(n^{2}+6 n+4\right)^{2}=m^{2}+16$. However, among the squares, only 0 and 9 have the form $a^{2}-16$; and since $m^{2}$ is odd, the sought square is $9=(-3)(-1)(1)(3)$.

[D. L. Silverman, M. M., 38, 60 (January 1965).]