# Problem 442: Eleven-free integers
An integer is called eleven-free if its decimal expansion does not
contain any substring representing a power of 11 except 1. For example,
2404 and 13431 are eleven-free, while 911 and 4121331 are not. Let E(n)
be the nth positive eleven-free integer. For example, E(3) = 3, E(200) =
213 and E(500 000) = 531563. Find E(1018).