[FOM] Problem on order types

JoeShipman@aol.com JoeShipman at aol.com
Fri Mar 4 23:27:02 EST 2005

Here's a cute problem.  The answer is a finite integer, but it's very easy to get it wrong.

Let X be an ordered set such that 
for all a<b in X, (a,b) is order-isomorphic to the rational numbers.

How many possibilities are there for the order type of X?

-- JS

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