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:

eban: {1_((x<)_,/(,/(2*!4)+/:10*0,3+!4)+/:1000*)/0}@_:

#eban 1000
19
#(1000>)_eban 4000
21
#eban 1e4
79
#eban 1e5
399
#eban 1e6
399
#eban 1e7
1599
#eban 1e8
7999
#eban 1e9
7999
#eban 1e10
31999
#eban 1e11
159999
#eban 1e12
159999
#eban 1e13
639999
#eban 1e14
3199999