Proof that an ordinal number does not contain itself
16971
Prove that no ordinal is an element of itself
2932
How do I prove this sum is not an integer
152516
How do we justify functions on the Ordinals
52861
Natural Numbers and Well ordering
35569
Prove that $[0,1]$ isn't homeomorphic to $\mathbb{R}$
139841
Proving $A\setminus(B\setminus C)$ is not equal to $(A\setminus B)\setminus C$
114043
Prove the existence of a real number satisfying a property
74546
Negating A Mathematical Statement
37783
Proving that a set of 2016 natural numbers contain a non-empty set with a sum divisible by 2016
70196
Is there any well-ordered uncountable set of real numbers under the original ordering?
118022
Show that a group of order $180$ is not simple.
3135
Is a limit ordinal necessarily a cardinal?
127362
How do I prove that there doesn't exist a set whose power set is countable?
63618
Can all ordinals be obtained by taking successors and countable limits?
32754
Each number in a subset $S\subseteq \{1,\ldots,2n\}$ does not divide another one. Then $\max |S|$?
36325
Embedding ordinals in $\mathbb{Q}$
129693
An interesting problem with "decomposing" natural numbers.