What's the cardinality of $\{ (i,j,k) : i+j+k=10, i,j,k \in \mathbb{N} \}$ ? General case.
94407
Number of solutions for $x[1] + x[2] + \ldots + x[n] =k$
109764
Find the cardinality of the quotient of $\mathbb R$ in respect to R
152342
$x_1+x_2+\cdots+x_n\leq M$: Cardinality of Solution Set is $C(M+n, n)$
85099
How many subsets of $\mathbb{N}$ have the same cardinality as $\mathbb{N}$?
15733
Show that the cardinality of $\mathbb N$ is the same as the cardinality of $\mathbb N \times \mathbb N$
122947
What is the cardinality of the set of infinite cardinalities?
156006
Cardinality of set containing all infinite subsets of $\mathbb{Q}$
149673
Cardinality of an infinite union of finite sets
109968
Let $X= \{ A \subset \mathbb{N} : \mathbb{N} \backslash A \text{ is finite}\}$. What is the cardinality of $X$? Prove it.
9651
Cardinality of cartesian product of an infinite set with N
959
Prove that ${{n}\choose{k}} = {{n - 2}\choose{k}} + 2{{n - 2}\choose{k - 1}} + {{n - 2}\choose{k - 2}}$.
73850
Cardinality of set of functions
48523
Let $A$ be any uncountable set, and let $B$ be a countable subset of $A$. Prove that the cardinality of $A = A - B $
113474
An $n \times n$ matrix $M$ of integers has the property that $M_{ab} = M_{xy}$ iff $a+b=x+y$. How many distinct elements are there in $M$?
98518
Cardinality of equivalence relations on N
46132
Combinatorial interpretation for the identity $\sum\limits_i\binom{m}{i}\binom{n}{j-i}=\binom{m+n}{j}$?
93330
Cardinality of all cardinalities