How many positive integers are there whose digits strictly increase from left to right?
+658 For example: 123 is the smallest 3 digit integer with digits strictly increasing left to right.
We list smallest numbers like cases in the example:
1 (does not count)
12
123
1234
12345
123456
1234567
12345678
123456789
Notice how for each of these cases. The number with \(n\) digits has \(10-n\) cases that fit the problem. Starting with the two digit numbers, the number of cases that fit the problem is 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = \(\boxed{36}\)
I'm not sure if this is correct, but it is my attempt on the problem.
