Prove the set $\Bbb Z^+ \times\Bbb Z^+ \times \Bbb Z^+$ is countable.
118595
Proving that a set is countable by finding a bijection
80096
Prove that the union of countably many countable sets is countable.
98284
show $\Bbb Z_6 \cong \Bbb Z_3 \times \Bbb Z_2 $.
15733
Show that the cardinality of $\mathbb N$ is the same as the cardinality of $\mathbb N \times \mathbb N$
17510
Proving a set is an abelian group.
99656
Prove that the set of all algebraic numbers is countable
9021
An infinite subset of a countable set is countable
154474
Image of countable and uncountable sets
4912
Show that an infinite set $C$ is equipotent to its cartesian product $C\times C$
40937
Is the set of partial order relations over $ \mathbb{N}$ countable?
23442
Cardinality of the union of infinite and countable sets
109219
How do the sets $\emptyset\times B,\ A\ \times \emptyset, \ \emptyset \times \emptyset $ look like?
54406
Is $\mathbb Q \times \mathbb Q $ a denumerable set?
90239
$\mathbb{Z} \times \mathbb{Z}$ is cyclic.
112933
Show that $Z\times Z$ is not cyclic...
52682
Is the power set of the natural numbers countable?
151295
Proving $|S \times \mathbb{N}|=|S|$ when $S$ is an infinite set