Do you seriously think a sane person would try to actually calculate that?

I'd say the answer lies in the order of millions or more, since you have all the possible front matches, multiplied by the number of all possible combination pairs of the other criteria (e.g. 2 base58 digits out of whatever many remain after the front digits). Then you scale down to some interval size and apply the approximations of a uniform distribution.

Also, this has zero relevance since I can assure you that whatever two numbers you ever provide, in whatever base you choose them to be, there is always some other common representation that makeswill make them look like they're siamese sisters. That's pretty much the case with all the "prefixes" of H160.

Do you seriously think a sane person would try to actually calculate that?

I'd say the answer lies in the order of millions or more, since you have all the possible front matches, multiplied by the number of all possible combination pairs of the other criteria (e.g. 2 base58 digits out of whatever many remain after the front digits). Then you scale down to some interval size and apply the approximations of a uniform distribution.

Also, this has zero relevance since I can assure you that whatever two numbers you ever provide, in whatever base you choose them to be, there is always some other common representation that makes them look like they're siamese sisters.