It is possible to construct simple functions which produce growing patterns. For example, the Baxter-Hickerson function f(n) = 1/3(2·10^(5n) - 10^(4n) + 2·10^(3n) + 10^(2n) + 10^n + 1) produces the sequence of numbers 64037, 6634003367, 666334000333667, ....

Baxter-Hickerson function | number pyramid