= Galaxy-conditioned neighbour count
{title2=$N(<R)=4\pi\bar n\int_0^R[1+\xi(r)]r^2dr$}
The mean number of other <galaxies> within distance $R$ of a randomly chosen <galaxy> is the integral of its conditional number density. A random location instead has mean count $4\pi\bar nR^3/3$. For a <power law> $\xi(r)=(r_0/r)^\gamma$, the extra count is $4\pi\bar n r_0^\gamma R^{3-\gamma}/(3-\gamma)$ when $\gamma<3$. The central <galaxy> is excluded; including it adds one. This distinction matters even when the unconditional mean number density is spatially uniform.
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