The Press–Schechter formalism predicts that the number of objects with mass between M and M + d M is: d n ≡ ≡ N ( M ) d M = 1 π π ( 1 + n 3 ) ρ ρ ¯ ¯ M 2 ( M M ∗ ∗ ) ( 3 + n ) / 6 exp ⁡ ⁡ ( − − ( M M ∗ ∗ ) ( 3 + n ) / 3 ) d M