Is there an equation $f(k,m,n)=n$ where $n$ is the number of applications of the Ackermann function needed?
86933
Ackermann function - how to calculate the number of times it calls itself
156542
Number of solutions to $a_1 + a_2 + \dots + a_k = n$ where $n \gt 0$ and $0 \lt a_1 \leq a_2 \leq \dots \leq a_k$ are integers.
94407
Number of solutions for $x[1] + x[2] + \ldots + x[n] =k$
69876
For every $n \in \mathbb{N}$, find a function $f$ which is differentiable $n$ times at $0$, but not $n+1$ times.
133101
Number of solutions of $P(x)=e^{ax}$ if $P$ is a polynomial
112575
Finding integer solutions of $m^2-n^5 = m - n$
71108
Is there an integer $N>0$ such that $\varphi(n) = N$ has infinitely many solutions?
19474
Find all solutions to the functional equation $f(x) +f(x+y)=y+2 $
108885
Systems of equations with a single number
24862
Solving (quadratic) equations of iterated functions, such as $f(f(x))=f(x)+x$
113360
How many injective functions $f:[1,...,m]\to{[1,...,n]}$ has no fixed point? $(m\le n)$
83346
Finding a closed form $x_n$ for the recurrence relation $x_{n+2} = px_{n+1} + qx_n + r$
78471
Closure of $\{\frac{1}{n}\}:=M$
14773
Finding distinct solutions for the equation
114379
Show that number of solutions satisfying $x^5=e$ is a multiple of 4?
112948
Fibonacci addition law $F_{n+m} = F_{n-1}F_m + F_n F_{m+1}$
146491
Number of solutions of $x_1+x_2+\dots+x_k=n$ with $x_i\le r$