  Using inequalities of Rosser and Schoenfeld, we prove formulas for pi(n) and
the n-th prime that involve only the elementary operations +,-,/ on integers,
together with the floor function. Pascal Sebah has pointed out that the formula
for pi(n) operates in O(n^(3/2)) time. Similar formulas were proven using
Bertrand's Postulate by Stephen Regimbal, An explicit formula for the k-th
prime number, Mathematics Magazine, 48 (1975), 230-23
