most recent 30 from http://mathoverflow.net 2013-05-21T23:56:36Z http://mathoverflow.net/feeds/user/30793 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/112651/how-many-well-orderings-of-aleph-0-are-there/119387#119387 Freddy Bustos 2013-01-20T07:06:34Z 2013-01-20T07:06:34Z

<p>The set of infinite binary sequences has size continuum. Each of that sequences determine uniquely a well ordering of N: let A and B, the inverse image of {0} and {1} respectively; let the set AUB whith the usual order in A and in B, and m &lt; n if m is in A and n is in B. So there are continuum many well-orderings of N that include the types w (if A is finite), all the w+n (if B is finite) and w+w (otherwise).</p> <p>How to assign a different type of order to each sequence with A and B infinite?</p> <p>Freddy William Bustos, 20 de enero de 2013</p>