Ambiguous definition of the set of Natural Number
33705
Is $0$ a natural number?
47720
Isomorphism from Natural numbers to the Odd Natural numbers
14512
Why cannot a set be its own element?
152547
Is the sum of all natural numbers countable?
22391
Is the set of all pairs of real numbers uncountable?
3217
Construction of uncountably many non-isomorphic linear (total) orderings of natural numbers
78294
How does one denote the set of  all positive real numbers?
123498
Is "empty set" an element of a set?
40662
What is the definition of a set?
81843
Sequences of sets property
858
Is $\{\emptyset\}$ a subset of $\{\{\emptyset\}\}$?
158842
What is wrong with this bijection from all naturals to reals between 0 and 1?
138569
Is the “sum of all natural numbers” unique?
2935
Completness and Set of Result of One Set ?!?
129693
An interesting problem with "decomposing" natural numbers.
121469
Proof of observations on natural numbers being expressed as differences of squares.
109305
Non-existence of natural numbers such that $\sqrt{n} +\sqrt{n+1} <\sqrt{x} +\sqrt{y} <\sqrt{4n+2}$