# Almost, just almost

Discrete Mathematics Level 4

We say that a number is almost increasing if for each digit of that number, either that digit is 0 or all digits to the left of it are (strictly) smaller than it. How many 4 digit numbers are almost increasing?

Details and assumptions

As an explicit example, the number $$2035$$ is almost increasing.

The number $$12=012$$ is a 2 digit number, not a 3 digit number.

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