= Einstein-de Sitter cumulative number counts
{c}
{title2=$N(<z_f)=\frac{8n_0c^3}{3H_0^3}[1-(1+z_f)^{-1/2}]^3$}
For constant <comoving number density> and complete selection in a spatially flat <Einstein-de Sitter universe>, integrate the present-epoch shell volume up to the population's formation <redshift>. The radial distance is $D_M=2c[1-(1+z)^{-1/2}]/H_0$, so the count per unit <solid angle> is $n_0D_M^3(z_f)/3$. It tends to a finite value as $z_f$ tends to infinity because this model's present comoving particle-horizon radius is $2c/H_0$. Formation, mergers or an incomplete observed sample change this ideal count.
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