I really like this problem, but I'm confused by one of the test cases. It asserts that num_count(2,2) is 90. If I'm reading that correctly, that means the number of two digit numbers without two successive zeros should be 90. But I can only think of one two digit number with two successive zeros: 00. Am I misinterpreting something?

Dear Ned,
num_count(2,2) == [10 : 99]
so total 2 digit numbers 'without' 2 successive zeros = 90 [since from 10 to 99, none of them contains 2 successive zeros].
now, '00' is not considered as a two digit number. similarly '023' is not considered as a 3 digit number.
I've considered the integer sequence here.

Am I wrong or is the problem actually requesting at least d-number of sucessive zeros? Having exactly d-number of sucessive zeros, and having at least d-number of sucessive zeros are two different cases. And the problem should specify which is the case required.