 Lower middle perversity

The lower middle perversity is $\bar{m}(k)=\lfloor (k-2)/2\rfloor$. The complementary upper middle perversity is $\bar{n}(k)=\lceil (k-2)/2\rceil$, and $\bar{m}(k)+\bar{n}(k)=k-2$. They agree at even codimensions.