Cantor's unspeakable numbers
Python 2, 77 75 74 70 bytes
Thanks to @MartinEnder for suggesting the limit of 9e5 which enderd up working after a change.Thanks to @mschauer for suggesting an infinite stream, saving 4 bytes.
def f(n=0):
 i=f()
 while 1:n+=1;yield next(i)if'7'in`n`or n%7&lt;1else n

This is a generator that yields an infinite stream of the numbers.