From the equation for uniform linear acceleration, the distance covered s = u t + 1 2 a t 2 for initial speed u = 0 , constant acceleration a (acceleration due to gravity without air resistance), and time elapsed t , it follows that the distance s is proportional to t 2 (in symbols, s ∝ ∝ t 2 ), thus the distance from the starting point are consecutive squares for integer values of time elapsed. The middle figure in the diagram is a visual proof that the sum of the first n odd numbers is n 2 . In equations: