When a=2, the value of b is 48 to 100, 53 kinds,

And so on

When a=48, the value of b is 2 to100,99 kinds,

When a=49, the value range of b is 1 to 100 and 100.

When a=50, the value of b ranges from 1 to 99,99.

When a=5 1, the value range of b is 1 to 98,98.

By analogy, when a= 100, the value range of b is 1 to 49,49.

That is, 52 to 100, then to 49, ***7498 species.