Counting Sums of Three Squares
Peter Shiu · Bulletin of the London Mathematical Society · 1988
Let Δ(x) be the error term associated with the asymptotic formula for the counting function on the set of numbers that are sums of three squares. We give a formula for Δ(x) and use it to prove that Δ(x) has average order and normal order 3 1og x/(16 1og 2).