How do I prove that this is onto - f : N → N × N?
67644
How does one get the formula for this bijection from $\mathbb{N}\times\mathbb{N}$ onto $\mathbb{N}$?
127400
Prove that ∀ n ∈ {n | n ∈ ℕ ∧ n > 7}: n = x*3 + y*5
4512
Is there a direct, elementary proof of $n = \sum_{k|n} \phi(k)$?
73454
Prove that $f$ has finite number of roots
1821
Proving $f(C) \setminus f(D) \subseteq f(C \setminus D)$ and disproving equality
49592
Show that, if $f:A\to B$ is a function, with $A$ and $B$ being finite sets, and $|A|=|B|$, then $f$ is one to one iff $f$ is onto.
128305
$PGL(n, F)=PSL(n, F)$
99782
$a_{n+1}=|a_n|-a_{n-1} \implies a_n \; \text{is periodic}$
75653
Prove that $|f ''|\ge 4$
121993
Prove that $f$ is one-to-one iff $f \circ h = f \circ k$ implies $h = k$.
61640
Prove c exists for f:[0,1] -> R
133017
Prove that $n^n>1\times3\times5\times7\times \dots\times(2n-1)$
14648
Show that $f_0 - f_1 + f_2 - \cdots - f_{2n-1} + f_{2n} = f_{2n-1} - 1$ when $n$ is a positive integer
9522
Proving $k \binom{n}{k} = n \binom{n-1}{k-1}$
21612
How to prove this form of $n$?
142534
Proof of $k {n\choose k} = n {n-1 \choose k-1}$ using direct proof
148500
Understanding this theorem and how to go about proving it surjectivity?