We say that an integer $n$ is abundant if the sum of the divisors of $n$ is at least $2n$. It has been known [wall71] that the set of abundant numbers has a natural density $A(2)$ and that $0.244 < A(2) < 0.291$. We give the sharper bounds $0.2474 < A(2) < 0.2480$.
"Bounds for the density of abundant integers." Experiment. Math. 7 (2) 137 - 143, 1998.