Density (Sequence)

Let a Sequence $\{a_i\}_{i=1}^\infty$ be strictly increasing and composed of Nonnegative Integers. Call $A(x)$ the number of terms not exceeding $x$. Then the density is given by $\lim_{x\to\infty} A(x)/x$ if the Limit exists.

References

Guy, R. K. Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 199, 1994.