Problem Statement

An   eban   number is a number that has no letter   e   in it when the number is spelled in English. Or more literally,   spelled numbers that contain the letter   e   are banned.

The American version of spelling numbers will be used here   (as opposed to the British). 2,000,000,000   is two billion,   not   two milliard.

Only numbers less than   one sextillion   (1021)   will be considered in/for this task. This will allow optimizations to be used.

Let's start with the solution: